Washington (CNN) - It's one of the storylines for 2012: Can the Democrats win back control of the House of Representatives?
A new poll suggests that they may have a chance.
According to a CNN/Opinion Research Corporation survey released Tuesday, the Democrats have a four-point margin over the Republicans in the battle for control of Congress. The poll indicates that 50 percent registered voters say if the election for Congress was held today, they would vote for the Democrat in their district, with 46 percent saying they would cast a ballot for the Republican in their district. The Democrats' four-point margin is within the poll's sampling error.
The GOP won 63 seats in last year's midterm elections, taking back control of the House for the first time in four years. CNN's last poll conducted before the midterms indicated the Republicans had a six-point advantage over the Democrats.
GOP victories in 2010 were due to some major historical shifts. More women voted for Republican candidates than Democratic candidates in 2010 for the first time since exit polling began in the early 1970s. Voters who never attended college - generally considered to be the bulk of the blue-collar vote - voted Republican in House races for the first time since 1994. And 56 percent of independents voted Republican in 2010, the highest that figure has ever been in exit polls.
"Now the Democrats are seeing some of their natural constituencies coming home," says CNN Polling Director Keating Holland. "In the latest generic ballot, Democrats have a ten-point lead among women, and a nine-point lead among voters who never attended college. But the Republicans still have a plurality of the Independent voters, 47 percent to 43 percent."
The poll also indicates a geographic split that may favor the Democrats, with Democratic candidates pulling a majority in the Northeast, Midwest and West. Republicans win a majority in the generic ballot only in the South.
"It's far too early to use these results to accurately forecast the 2012 congressional elections," Holland notes. "But it does indicate that some of the shifts that swept the GOP into power in 2010 may be shifting back."
The generic ballot question asks respondents if they would vote for a Democrat or Republican in their congressional district, without naming any specific candidates. It's used by many polling organizations, including CNN/Opinion Research Corporation surveys.
The CNN/Opinion Research Corporation poll was conducted April 29-May 1, with 1,034 adults questioned by telephone. All interviews were completed before news of Osama bin Laden's death was reported. The survey's overall sampling error is plus or minus three percentage points.
– CNN Deputy Political Director Paul Steinhauser contributed to this report.