Barack Obama has regained the lead over John McCain in Colorado and has maintained his lead in the three other battleground states being followed by the Quinnipiac University poll.

Obama is favored by 49 percent of likely voters in Colorado, versus 45 percent for McCain.

McCain had held a one-point lead in Colorado in late August.

The poll of 1,418 likely Colorado voters, taken Sept. 14-21, has a margin of error of plus or minus 2.6 percentage points.

Obama leads by four points in Michigan, two points in Minnesota and seven points in Wisconsin.

And Democratic U.S. Senate candidate Mark Udall broke a tie with Bob Schaffer, leading the Republican by 8 percentage points in the September poll.

"Two years ago when the Democrats picked Denver for their convention, one of the main reasons was the hope it would help them win Colorado, which is shaping up as a key state in the Electoral College," said Peter Brown, assistant director of the Quinnipiac University Polling Institute. "Sen. Obama has come from behind to take the lead there and it is a reasonable assumption that the convention has something to do with this," Brown said.

The poll, conducted in conjunction with the Wall Street Journal and Washington Post, found that those polled chose Obama as the "candidate of change" by wide margins.

"With a lousy economy, an unpopular war and an even less popular Republican president, it's difficult to find voters who don't want change," Brown said.

Obama has made himself the candidate of change by "joining Senator McCain at the hip with President George Bush," and sharply defining himself as the antithesis of the president, Brown said.

The Wall Street meltdown happening while the polling was being done likely "fed the public desire for change and seemed to benefit Senator Obama."

Despite Sarah Palin's explosion onto the scene, more voters in each state said they would rather see Democratic vice presidential candidate Sen. Joe Biden become president than Palin.

They did say McCain's selection of the Alaska governor was a good choice.

By a 49 percent to 42 percent margin, Colorado voters would rather see Biden as president. Women pick Biden 52 percent to 37 percent, while men go 46 percent to Palin and 45 percent Biden.

Obama holds a 15-percentage-point lead among Colorado women, while men prefer McCain by seven points, the poll said.

White voters in Colorado favor McCain by seven points, while Hispanics here give Obama a 42-point margin.

Obama has a 10-point lead among Coloradans 35 to 54 years old.

Younger voters are split evenly among the two candidates, while those 55 and over favor McCain by a single point.

Just over half of the Coloradans surveyed said the economy is the most important issue in the election.

Colorado voters gave Obama the nod — by six points — on which candidate better understands the economy.

McCain had a big lead — 34 points — among Coloradans on who better understands foreign policy.

Obama's lead shrunk a couple points in Wisconsin — to seven points — and he maintained his two-point margins in Michigan and Minnesota.