Republican presidential nominee Sen. John McCain's post-convention bounce in the polls appears to be over, as a series of national polls in recent days show that Democratic nominee Sen. Barack Obama has regained his lead.

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Obama has taken a 48-43 percent lead over McCain in the latest CBS News/New York Times poll released Thursday. McCain had a 2 percentage point lead in the same poll on Sept. 8, after the Republican National Convention. Before both party's conventions, Obama led McCain.

The latest Qunnipiac University poll, also released Thursday, has Obama leading McCain 49-45 percent among likely voters nationwide. Qunnipiac attributed Obama's lead to a 14-point edge among women and a 91-point lead among blacks compared to McCain.

Reuters/Zogby International also cited Obama's strength among women voters when compared to McCain in its latest poll, which gives the Democrat a 47-45 percent lead over his Republican rival.

The Republican convention, with its introduction of Alaska Gov. Sarah Palin as the party's vice presidential nominee, was a boon to McCain. USA TODAY/Gallup Poll, taken right after the convention, showed McCain leading Obama by 50-46 percent among registered voters. In a similar poll the week previously, Obama held an edge over McCain of 7 percentage points.

The addition of Palin to the ticket led 29 percent of voters to say they were more likely to vote for McCain, while 21 percent said they were less likely, USA TODAY/Gallup Poll said.