For Democrats, one of the biggest problems with the protracted presidential race is that Sen. John McCain has been able to organize his general election campaign and begin to define himself to the nation without much interference.

But what should be more troubling to Democrats is how McCain is also gaining the upper hand by engaging Sen. Barack Obama. In almost daily attacks, he's drilled the Democratic frontrunner on his relationship with the Rev. Jeremiah Wright and former Weather Underground member Bill Ayers.

There are two main reasons for doing this:

1. He's energizing a Republican base that's never really been on board. Attacking a Democrat is one of the best ways for McCain to prove himself to this group of voters.
2. He's signaled to the Obama campaign that the general election will be a tough one. By getting Obama to respond to him almost daily, he helps undercut the argument that the Illinois senator is "above the fray" and running on a "new kind of politics."
   

As First Read notes this morning, however, the "downside to McCain’s tough tone, of course, is that it's very un-McCain. This isn’t the same guy we saw in 2000 or even in the GOP primaries... Indeed, this tack can turn off folks (especially those coveted independents) as much as it might hurt Obama."

A Political Wire reader runs the math and notes that before the Pennsylvania, Sen. Hillary Clinton needed to get at least 63% of the vote in the remaining states to have a chance to win more delegates than Sen. Barack Obama.

Clinton now needs 296 of the remaining 435 delegates up for grabs (or approximately 68% of the vote.) In contrast, Obama needs 140 of the remaining 435 to have the majority (or about 32% of the vote.)

Therefore, despite her win in the Keystone State, the results have in fact made it less likely Clinton can win.

Considering that most polls predict Obama should win North Carolina by a healthy margin and both campaigns think Indiana will be close, the chances of a Clinton victory are actually lower than ever.

Nearly every poll shows Sen. Hillary Clinton on her way to a victory over Sen. Barack Obama in the Pennsylvania primary. We won't fall into the trap of poll averaging, but will instead list the most recent polls here:

• Zogby: Clinton +10
• SurveyUSA: Clinton +6
• Suffolk: Clinton +10
• Quinnipiac: Clinton +7
• Strategic Vision: Clinton +7
• American Research Group: Clinton +13
• Mason-Dixon: Clinton +5
  
• Public Policy Polling: Obama +3
  

As in all elections, the results tonight will depend on turnout. In fact, the difference in the polls above are almost entirely on how they predict turnout.

Should Clinton win Pennsylvania by five points or less, it will widely be interpreted as an indication her voters stayed home. If she wins by double-digits, it will be due to her supporters flocking to the polls. To reasonably continue her campaign of convincing superdelegates about her electability, Clinton needs a big victory.

Meanwhile, as Ben Smith notes, Obama couldn't have had a worse few weeks. He's been on the defensive, had his worst debate performance of the campaign and seems more interested in running out the clock on Clinton than inspiring his own supporters. His attacks on Clinton over the last few days are an obvious attempt to get Clinton voters to stay home.

So after 15 months of campaigning, the Democratic presidential nomination fight comes down to Clinton's margin of victory in Pennsylvania. A 10+ point lead will be seen as a big Clinton win while anything less than five points will be a big Obama win. However, if Clinton's victory is between five and 10 points, the campaign continues.

With dozens of new polls out every week, it's tempting to use polling averages -- such as those used by Real Clear Politics -- to smooth out the many results and hopefully make them more understandable.

But as I noted several months ago on Political Wire, there are many reasons poll averaging doesn't work:

• Surveys are in the field at different times -- often over several days -- so respondents are not always aware of the same recent events.
  
• Each poll typically uses different methodologies for forecasting turnout. 
• Polls have different sample sizes, yet when they're averaged they are usually are weighted the same.
  
• Pollsters use different screens to determine likely voters.
  
• Some pollsters use telephone surveys while others use robocall surveys.
  
• The wording of questions on surveys can differ which can wildly skew results.
• Some of the pollsters included in the polling averages are just not reliable.
  

While doing a simple average can eliminate some of the biases noted above, the technique may also magnify them dramatically. As a result, the polling average can be more unreliable than the original polls themselves.

There are several key signs that Sen. Barack Obama is managing to contain the damage of his ill-timed "bitter voter" comments made last Friday.

1. With the exception of a controversial ARG poll, most polls in Pennsylvania -- such those from Quinnipiac and  Susquehanna -- show no serious erosion of his support.
2. A new SurveyUSA poll shows most voters in Harrisburg were not offended by Obama's remarks.
   
3. National tracking polls show Obama holding a steady lead over Clinton.
4. Though she holds a solid lead in nearly every Pennsylvania poll, the Clinton campaign released a risky negative ad to highlight the controversy.

Chuck Todd argues we won't fully know if Obama has weathered the storm until after the Pennsylvania, Indiana, and North Carolina contests, but the early indications look good for Obama.

It's impossible to predict exactly how Sen. Barack Obama's ill-timed comments about "bitter voters" in Pennsylvania and the Midwest will ultimately play out in the Democratic presidential race. The comments certainly make Obama seem elitist and distant from the daily concerns of stereotypical Midwesterners. And Sen. Hillary Clinton correctly points out that both Al Gore and Sen. John Kerry lost the last two presidential races because they were "out of touch" with concerns of "regular" voters. Undecided Democratic superdelegates must be very worried.

But Obama does have one thing going for him as he tries to weather the controversy: Clinton connects no better with your average small town, rural voter than he does. She looks absolutely ridiculous trying to become the church-going, gun-toting candidate before crucial primaries in Pennsylvania and Indiana. If she continues to push this line of attack, it's more likely to backfire than succeed.

Update: At a speech in Pittsburgh today, Clinton continued her attacks on Obama as an "elitist" but her remarks were met with "quite a few murmurs" and then groans, according to First Read.

Sen. Barack Obama recently hinted that he might break a promise and opt out of public financing for the general election because he's already "created a parallel public financing system where the American people decide if they want to support a campaign they can get on the Internet and finance it."

Meanwhile, Sen. John McCain, who has been badly outraised by Obama -- and Sen. Hillary Clinton too -- is trying to turn his disadvantage into an advantage by laying the groundwork to accept public money and chiding Obama for failing to do so. (Left unmentioned in McCain's rhetoric is that the RNC's general election fund is likely to dwarf that of the DNC.)

While forgoing public financing would certainly be an embarrassment for Obama, he might go ahead anyway. The most obvious reason is that he's already built a fundraising powerhouse that dwarfs his rivals. But he might also have a point about creating a better system of public financing.

For instance, Obama could easily turn a flip-flop story to his advantage by pledging to cap all campaign contributions at $250. Harnessing new voters, his popular brand and the Internet, he could promise to really build a people-based campaign. A million individuals could literally "max out" and feel like they have just as much influence as anyone else.

If you read Obama's statement closely, he may have even hinted at this -- although Marc Ambinder reports a campaign official says they have not even considered the idea.

It's not without risks, but if Obama did choose to cap contributions there's no way McCain could match him and still be competitive.

Last week, we noted the Democratic primary race in Pennsylvania is turning into a race with polls showing Sen. Hillary Clinton's lead over Sen. Barack Obama slipping to the single digits.

Here are the four main reasons why the race is tightening:

• Obama brought in seasoned staffers to organize the state.
  
• He is flooding the airwaves with advertisements at an unprecedented level.
• His six day bus tour was well covered across the state and coincided with a key endorsement from Sen. Bob Casey (D-PA).
• Clinton campaign mismanagement has been a huge story over the last week, undermining one of her key message points.

It's important to note that nearly every poll still shows Clinton ahead. But it's clear Obama has made the Keystone State primary a race to watch.

The presidential campaign shifts from the roads of Pennsylvania and North Carolina to Capitol Hill on Tuesday when Gen. David Petraeus and and Ambassador Ryan Crocker testify on the Iraq war before the United States Senate. With television cameras catching every moment, the Q&As with Sen. John McCain, Sen. Barack Obama and Sen. Hillary Clinton should offer insight into the candidates' thinking on the war and how they would deal with those in charge.

McCain and Clinton will be asking questions as members of the Senate Armed Services Committee, where McCain is the most senior Republican. Obama will be asking questions at a separate Senate Foreign Relations Committee hearing scheduled later in the day.

Here's some pre-game handicapping:

• McCain scores points if he can make it clear that his support of the troop surge last year paid off with less violence in Iraq. He will be relentless in highlighting the positives of the Bush administration strategy -- and as a result, his own wisdom in supporting the president.
  
• No candidate has more on the line than Clinton. She needs to be the toughest, most intelligent questioner to bolster her argument that she will be "ready on day one" to become Commander in Chief. But she also needs to prove to Democrats voting in the next few states that she is committed to ending the war.
  
• Expect Obama to play it safe. He needs to come across as intelligent and ready, but it's more important that he make no mistakes that could cause Democratic superdelegates to re-evaluate him as a candidate. Having the stage to himself at a different committee hearing should be an advantage.
  

Sen. Hillary Clinton's presidential campaign released seven years of tax returns Friday afternoon just after 4 p.m. Tactically, it's a perfect time to release them -- especially if there's any controversial news in the documents.

1. News coverage will continue to focus on the 40th anniversary of the Martin Luther King, Jr. assassination.
2. There are still more than two weeks until the Pennsylvania primary. 
3. It buries the story about chief strategist Mark Penn's conflicts of interest.
4. Many people are more interested in watching the Final Four and first weekend of baseball season.
   
5. It's Friday.
   

Just two weeks ago, polls found Sen. Hillary Clinton way ahead of Sen. Barack Obama in Pennsylvania -- with a few even showing her in front by more than 20 points. Some strategists suggested Obama skip the race and head to North Carolina where he has a more natural constituency.

In the last few days, however, new surveys show Clinton's lead collapsing in a dramatic fashion. Take a look at the most recent polls:

• Insider Advantage: Clinton +2
  
• Strategic Vision: Clinton +8
• Public Policy Polling: Obama +2
• Quinnipiac: Clinton +9
• SurveyUSA: Clinton +12
  

The primary is still two weeks away -- and polls haven't always been reliable during this primary season -- but we can now expect the media to treat this race as a real showdown.

Last week in an interview, Senate Majority Leader Harry Reid declared it would be "easy" to settle the Democratic presidential race before the late summer convention. He said he had a conversation with DNC Chairman Howard Dean and noted "things were being done."

Today, we learn more about the Reid-Dean master plan to settle the race: They asked Democratic superdelegates to make up their minds by early July.

If that's it, Democrats should be worried about the lack of leadership in their party. In fact, a New York Times suggests Democratic insiders are concerned that Dean doesn't have the clout to successfully navigate a peaceful end to the primary race.

With Al Gore staying on the sidelines, it's clear there are no power brokers left in the Democratic party.