In Wisconsin and New Hampshire, Romney remains within striking distance, even as the number of undecided voters shrinks, results from the poll released Wednesday indicated.
Obama has a 49 percent-to-46 percent edge in Wisconsin among likely voters -- half what his lead was two weeks ago -- and a 49 percent-to-47 percent lead in New Hampshire, down from a 7 percentage points in September.
In Iowa, Obama led Romney by 50 percent to 44 percent lead among likely voters.
Lee Miringoff, director of the Marist Institute for Public Opinion, which conducted the surveys, said Obama's numbers hovering around 49 percent or 50 percent in the three swing states gave him a notable edge, but not a sizeable one.
"But he doesn't have to look that far over his shoulder to see that half the electorate is not with him and that Romney is close," Miringoff said.
The polls of more than 1,000 likely voters in each state were conducted on Sunday and Monday. The margin of error was 3 percentage points in Wisconsin, 3.1 percentage points in New Hampshire and 2.9 percentage points in Iowa.