Yet more swing state polling shows President Obama asserting a lead, with a trio of polls from NBC News and Marist College showing him at the all-important 50 percent mark in Colorado, Iowa and Wisconsin.

The polls show Obama leading Mitt Romney 50 percent to 45 percent in both Colorado and Wisconsin and 50 percent to 42 percent in Iowa. (The Wisconsin poll also showed Democratic Rep. Tammy Baldwin gaining in that state's important Senate race. She's now at 48 percent, compared to Republican former governor Tommy Thompson's 46 percent.)

The surveys come on the heels of a string of swing-state polls showing the president expanding his leads in the states that will decide the presidency.

Since the end of the conventions, nearly two dozen non-automated swing state polls have shown Obama leading — often by four or more points. No live interview poll has shown Romney leading in any of the nine states generally viewed as toss-up states.

A new North Carolina poll from High Point University on Friday also showed the president leading in that state, 48 percent to 44 percent.

And a CNN/Opinion Research poll released Thursday showed the president leading in Nevada 49 percent to 46 percent.

At the same time, the Gallup daily tracking poll continues to show the race tied nationally. In contrast, a Heartland Monitor/National Journal poll released Friday showed Obama leading by seven across all 50 states.