Poll Tracker

"The Democrats' dimmer electoral prospects are more a matter of disillusionment with the party that controls Congress than a revival of the image of the Republican Party," Pew said in explaining its results. "Favorable ratings of the GOP remain quite low (40%), even as opinion of Democrats has soured; just 48% say they have a favorable opinion of the Democratic Party, down 11 points since April."

Pew attributes the Democrats' change in fortunes to a defection by independent voters who had supported them by 11 percentage points just before the 2008 election but now would favor a Republican candidate in their district by 43 percent to 38 percent.

While Democrats still lead on how they would handle certain issues and on personal traits, such as honesty, they have lost ground since last year. On average in February 2008 Democrats outpaced Republicans by more than 20 percentage points. Now that figure is just above 12 percentage points.

And Pew also found that the more people heard about the proposals to overhaul the health care system, the less likely they were to like it.

People who have heard a lot oppose the plans 55 percent to 38 percent, and those who have heard little, favor them 41 percent to 36 percent, with 23 percent expressing no opinion.

For those who oppose the health overhaul, they tend to do so with more intensity that those who support them, with 34 percent saying they oppose them "very strongly" and 25 percent saying they support them "very strongly."

But they still like President Obama, with 56 percent saying they have a great deal or a fair amount of confidence in him.

The survey was based on interviews by telephone in English and Spanish with 2,003 adults nationwide and carries a margin of error of plus or minus 2.5 percentage points.