CNN

CNN's breakdown of the electoral college map.

(CNN) - A set of polls released Thursday shows Barack Obama leading John McCain in four critical battleground states - Michigan, Wisconsin, Colorado and Minnesota.

A new Quinnipiac University/Wall Street Journal/Washingtonpost.com survey put Obama up significantly over the Arizona senator in Minnesota - 54-37 percent – and Wisconsin - 52-39 percent. His lead is smaller in Colorado - 49-44 percent - and Michigan - 48-42 percent.

This comes on the heels of another Quinnipiac poll last week that had Obama leading in the key swing states of Ohio, Pennsylvania and Florida.

In a briefing on Wednesday, Obama campaign manager David Plouffe explained the campaign's strategy to reach the 270 electoral votes needed to win the presidency. The campaign is counting on winning the 20 states John Kerry won in 2004, looking to add Iowa, and then setting their sights on several others. Among those: the four states included in Thursday's poll.

Watch: CNN's John King breaks down the electoral map

Plouffe said Michigan is one of the most competitive states, attributing its competitiveness to the fact that Obama didn't campaign or run ads there in the primary. He claimed they are "very strong" in Colorado and "very competitive" in Wisconsin and Minnesota.

The poll surveyed between 1,300 and 1,600 likely voters from June 17-24 with margins of error of plus or minus 2.5 percent for Minnesota and Wisconsin, 2.6 percent for Michigan and 2.7 percent for Colorado.

The latest CNN national poll of polls has Obama up 48-40 over McCain among registered voters nationwide.