September 14, 2012 7:00 AM

(CBS News) With the parties' conventions over and Election Day just weeks away, President Barack Obama has a three-point edge over Republican Mitt Romney among likely voters nationwide in the latest CBS News/New York Times poll.

Forty-nine percent of likely voters said they'll vote for Mr. Obama, 46 percent said Romney and 4 percent said they're undecided in the poll conducted from Sept. 8-12.

This is the first national poll in which CBS News and the New York Times have measured the presidential race among likely voters. The measure for likely voters takes into account voters' reported intent to vote, voting history and other factors that historically affect an individual's decision to vote.

President Obama has a wider lead over Romney among the broader group of registered voters nationwide. 51 percent say they'll vote for Mr. Obama (the first time he is above the 50 percent mark), while 43 percent choose Romney. Heading into the parties' conventions, the President and Romney were neck and neck among registered voters.