McCain, R-Ariz., who likely will face Democrat Sen. Barack Obama of Illinois in November, leads Obama in Colorado, while narrowing the gap since June 26 in Minnesota, Michigan and Wisconsin, Quinnipiac University polls show.

In Colorado, McCain leads Obama 46 percent to 44 percent. In Michigan, Obama leads McCain 46 percent to 42 percent, while in Minnesota Obama narrowly leads McCain 46 percent to 44 percent. In Wisconsin, Obama leads McCain 50 percent to 39 percent.

"Senator Barack Obama's post-primary bubble hasn't burst, but it is leaking a bit. It's been a good month for Senator John McCain. His movement in these key states, not large except for Minnesota, jibes with the tightening we are seeing in the national polls," said Peter Brown, assistant director of the Quinnipiac University Polling Institute.

"The good news for McCain is that he has improved his standing in Colorado and Michigan, two states that are critical to each man's strategy," Brown added.

The polls are based on surveys conducted July 14 to July 22. The maximum margin of error for the polls is about plus or minus 2.5 percentage points. The state sample sizes range from 1,094 to 1,984 likely voters.