Elaine Marshall, North Carolina's secretary of state, announced Wednesday that she has taken the first official step to launching a bid against Republican Sen. Richard M. Burr -- giving the Democrats the top-tier challenger they have sought for one of their targeted 2010 Senate takeover bids.

Marshall filed paperwork with state officials establishing her intention to run. And Marshall campaign adviser Thomas Mills said the response in the 24 hours since has been "bigger than we thought."

"We just about couldn't handle what came in yesterday," Mills said of the donations, phone calls and e-mails pouring in to Marshall's nascent campaign. Democrats, he said, "want to have somebody to get behind against Burr."

Freshman Rep. Larry Kissell, who captured the seat in North Carolina's 8th District for the Democrats in 2008, has drawn a Republican challenger: Lou Huddleston, a businessman and retired U.S. Army colonel, who announced his candidacy Wednesday.

A 31-year Army veteran, Huddleston appears a long-shot as he enters the contest. He lost his only previous bid for public office, a 2008 state House race, to incumbent Democrat Margaret Dickson. But Republicans think he has the potential to become a credible challenger to Kissell, given his resume as a military man and a local business leader, as well as the fact that he is African-American. African-Americans make up more than a quarter of the 8th district electorate.

Huddleston appears to be the GOP's man in the 8th District, which the GOP says is its top target in the state, after other recruits decided to pass on the race. Former five-term Rep. Robin Hayes -- who lost a 2008 rematch to Kissell by 55 percent to 45 percent in 2008 after winning their 2006 contest by a razor-thin margin -- announced last Wednesday that he would forgo a comeback bid.

The third time won't be a charm for former North Carolina Republican Rep. Robin Hayes, who is passing up a re-rematch against freshman Democrat Larry Kissell.

Hayes, who defeated Kissell by just 329 votes in 2006 and then lost to him in 2008 by a margin of almost 10 times that number (30,551 votes, to be precise), announced Wednesday that he would not try to regain his 8th District seat in 2010, the Associated Press reported.

Instead, Hayes told the AP, he plans to play a behind-the-scenes role in the campaign.

Hayes' decision doesn't mean that Kissell has an easy path back to Capitol Hill. Although he currently lives just outside the 8th District boundaries, Pat McCrory, the longtime mayor of Charlotte, has been mentioned as a potential top-tier GOP challenger. He is already well known outside the city; in the 2008 gubernatorial campaign, McCrory ran a highly competitive (but ultimately unsuccessful) race against Democrat Bev Purdue.

In a sign of Republican concern over Sen. Richard Burr's re-election chances, Burr's friend and Senate colleague, John McCain, is now running Google ads pumping the North Carolina freshman.

As first spotted by the Charlotte News and Observer, a Google search of "Richard Burr" brings up a sponsored link from McCain's Country First political action committee -- "Richard Burr NC Senator," it reads, followed by "Join John McCain's Country First to Support Candidates like Burr!"

The link leads to the PAC's Supported Candidates page.

North Carolina Sen. Richard M. Burr has been vocal this week, as he spearheads a home-state battle against a bill on the Senate floor that would allow the federal Food and Drug Administration to regulate tobacco products.

But the first-term Republican, who is seen as vulnerable to a challenge in his 2010 re-election contest, had less to say on Thursday about speculation over which Democrat will seek to take him on next year.

"We're on track with what we have planned to raise, and structurally have put the campaign together," said Burr, who reported $1.6 million in cash on hand in his campaign account as of the end of March.

He acknowledged that he has been targeted for defeat by Democratic strategists, saying, "I'm sure with the bounty that the Democratic Senatorial [Campaign] Committee has on my head, I won't go unopposed."