(CBS News) -- Mitt Romney has seen his lead over President Obama increase slightly in a new national poll of likely voters. The Gallup Daily Tracking poll gives Romney a six point advantage over Mr. Obama, with 51 percent of respondents saying they'd vote for Romney and 45 percent backing the president.
This is the third day Romney has seen a slight increase in his lead in the poll, which surveyed 2,700 likely voters and has a 2-point margin of error. The survey was taken before last night's presidential debate.
A new poll in Wisconsin, meanwhile, shows the race between Mr. Obama and Romney tied. The president garnered 49 percent among likely voters compared to Romney's 48 percent in the Marquette Law School poll. The survey shows a tightening race between the two candidates: Mr. Obama had an 11 point lead in the same poll just two weeks ago, prior to the first presidential debate.
The results echo a CBS News poll released last week, where Mr. Obama had a three point lead in the Badger State -- smaller than the 6 point lead he had in the state in September.
Marquette's survey suggests that the first presidential debate, which Romney is widely considered to have won, had an impact on Wisconsinites. Romney led by two points among those who watched the debate, while Mr. Obama led by 12 points among those who did not. The poll included interviews with 870 likely voters, and has a 3.2 percent margin of error.
Mr. Obama still has the support of young voters, according to a new national poll of voters aged 18 - 29 conducted by Harvard's Institute of Politics. The survey's findings reveal that Mr. Obama leads Romney by 19 points among this group, with 55 percent backing the president compared to 36 percent backing Romney.
Only 48 percent of respondents say they will "definitely" vote, however -- bad news for a president who won in 2008 in part on the strength of a surge in young voter turnout. The poll also found that enthusiasm for Mr. Obama is lower than for Romney. Sixty-five percent of Romney voters say they would "definitely" vote, while only 55 percent or Mr. Obama's voters say they will.
The poll surveyed 2,123 young voters between September 19 and October 3. It has a 2.1 percent margin of error.