Republican Sen. Norm Coleman has widened his lead over DFL challenger Al Franken, according to a telephone poll taken Tuesday of 500 likely Minnesota voters.

According to Rasmussen Reports poll results released Thursday, 50 percent of the respondents said they favored Coleman for a second term in the U.S. Senate, while 43 percent said they backed Franken.

The results were within the margin of sampling error of plus or minus 4.5 percentage points, meaning the contest may be closer than the numbers suggest. It also means Coleman may have a bigger lead than the poll shows.

The poll didn't test Coleman's strength versus the other DFL challenger, University of St. Thomas Prof. Jack Nelson-Pallmeyer, who is vying with Franken for the party's endorsement at its state convention in June.

But the numbers are going in the right direction for Coleman, who last month had a two-point lead over Franken in the same poll. The February Rasmussen Reports poll had Franken ahead of Coleman, 49 percent to 46 percent.

In this week's poll, with the 4.5-percentage point margin of error factored in, Coleman's support could be as high as 54.5 percent or as low as 45.5, while the range of support for Franken could be from a low of 38.5 percent to a high of 47.5.

In presidential politics, the poll found that Democratic candidates Barack Obama and Hillary Clinton appear to be pulling away from presumptive Republican nominee John McCain in Minnesota.

According to the poll, Obama is leading McCain 52 percent to 38 percent, while Clinton's lead over McCain is 47 percent to 42 percent. Past Rasmussen polls have had McCain running even with Obama and Clinton.

Pollsters also asked respondents to rate Gov. Tim Pawlenty's performance. Fifty-five percent said they believed the Republican governor was doing a fair or poor job, while 44 percent rated his performance as excellent or good.