The polls just keep on coming.

A new poll of Minnesotans shows Democratic presidential nominee Barack Obama back on top of Republican John McCain in a state both campaigns regard as vital to victory in November.

The poll, released Monday and conducted late last week by Rasmussen Reports, shows Obama ahead 52 percent to 44 percent. The poll has a margin of sampling error of plus or minus 4.5 percentage points.

Separately, the American Research Group released a poll Monday showing Obama with a 1-percentage-point lead, a statistical tossup.

The surveys come at a time when other polls have recently found that Obama's once-healthy lead in a reliably Democratic race had either diminished or disappeared.

Earlier this month, the Star Tribune's Minnesota Poll showed the race tied, with both candidates supported by 45 percent of the state's likely voters.

The Rasmussen firm also released a poll on the Minnesota U.S. Senate race Monday, showing the race between Republican incumbent Norm Coleman and Democratic challenger Al Franken virtually tied.

In the survey, Coleman has 48 percent to Franken's 47 percent, a statistically insignificant difference. Independence Party candidate Dean Barkley registered 3 percent support.

Other recent polls also show a close race, but Barkley had double-digit support in two of them.