Washington (CNN) - Democrats face a growing enthusiasm gap in this year's battle for Congress, according to a new national poll.
The CNN/Opinion Research Corporation survey released Friday also indicates Americans are split in their choice for Congress in November's midterm elections, with Republicans making gains at the Democrats' expense.
Forty-nine percent of Republicans questioned in the poll say they're extremely or very enthusiastic about voting this year, up 6 points from November. Thirty-one percent of Democrats say they're enthusiastic, down 11 points.
"Democrats face a huge 'enthusiasm gap,' and that gap is growing," says CNN Polling Director Keating Holland. "But the poll indicates that roughly half of all registered voters may change their minds between now and Election Day, so there is plenty of time for the playing field to change."
According to the survey, 48 percent of registered voters say they would vote for the Republican candidate for Congress, with 45 percent saying they'd back the Democrat. The 3-point edge for the GOP is within the poll's sampling error - but it's a switch from November, when the Democrats held a 50 to 44 percent advantage. The generic ballot question asked respondents if they would vote for a Democrat or Republican in their congressional district, without naming any specific candidates.
"That 3-point difference doesn't sound too bad for the Democrats, but the party's numbers are boosted by high levels of support in districts that the GOP has no chance of winning this year," says Holland. "In safe Democratic districts, the Dems have a 21-point advantage over the GOP."
The poll paints a different picture in more competitive districts, those where the incumbent won with less than 55 percent of the vote in 2008. In those districts, the poll indicates Democrats are currently facing a 27-point deficit, with 59 percent of registered voters in the competitive districts now saying they would vote for the Republican candidate for U.S. House if the election were held tomorrow, and only 32 percent that they would choose the Democratic candidate.
"That suggests big losses for the Democrats this November. But keep in mind that there is a lot of white noise in the data, because it is almost impossible to accurately model individual House districts," adds Holland.
The poll indicates that 2010 is shaping up to be a bad year for incumbents regardless of party. Just a third of all Americans say they would prefer to vote for an incumbent this year than a challenger, with 46 percent saying they would rather vote for the challenger and one in five adding that it makes no difference.
"Those numbers are roughly the same as they were at the start of 1994, when the Democrats lost control of the House. Challengers are seen as more honest than incumbents, more likely to bring change, and more likely to represent the views of the voters," says Holland.
The CNN/Opinion Research Corporation poll was conducted January 8-10, with 1,021 adult Americans questioned by telephone. The survey's overall sampling error is plus or minus 3 percentage points.
Democrats currently hold a 256-178 advantage in the House of Representatives, with one seat formerly held by the Democrats vacant. The GOP needs to win back 40 House seats in November to regain control of the chamber.
–CNN Deputy Political Director Paul Steinhauser contributed to this report
Follow Paul Steinhauser on Twitter: @psteinhausercnn