The percentage that describes themselves as Democrats has fallen five points this year, according to Rasmussen. There are still, according to the poll, more Democrats than Republicans: 33.1 percent of Americans say they are members of the GOP. But the 2.9 point gap between the two is the smallest it has been since December 2007.
The percentage of American adults unaffiliated with either party has increased one-half point from last month. It now stands at 30.8 percent in the poll.
The slide in party identification is not good news for Democrats, including President Obama, who has seen his approval rating fall below 50 percent in Rasmussen polling. The drop comes in part because of increasingly skeptical views of his handling of the war in Afghanistan and health care reform.
In the two years before Democrats made dramatic gains in Congress in the 2006 midterm elections, their party identification advantage grew 4.5 percentage points. It grew another 1.5 percentage points between the 2006 and 2008 elections. The recent trend in which the gap has closed could portend trouble for Democrats in the 2010 midterm elections, a contest in which the president's party traditionally loses seats.
The figures are a measure of all American adults, not likely voters.