Forty-two percent (42%) of U.S. voters believe that Republican Senator Arlen Specter’s switch to the Democratic Party will have a significant impact on the laws passed by the Senate.

Twenty-five percent (25%) say the Pennsylvania senator’s change of parties will not have a major impact, and 33% are not sure, according to a new Rasmussen Reports national telephone survey.

Fifty-one percent (51%) of Republicans believe Specter’s move will have a significant impact on legislation in the Senate, compared to 42% of Democrats and just 32% of voters not affiliated with either major party.

Specter’s decision is likely to give Democrats a 60-member filibuster-proof majority in the Senate if the Minnesota Supreme Court, as expected, upholds the victory of Democratic Senate candidate Al Franken in that state.

Just 25% of voters have a favorable impression of Specter, including six percent (6%) whose view is Very Favorable. Fifty-three percent (53%) regard the longtime senator unfavorably, with 27% whose opinion of him is Very Unfavorable. However, 22% apparently don’t know enough about the 29-year Senate veteran to have an opinion one way or the other.

Democrats have a much higher regard for Specter than Republicans. While 41% of Democratic voters view the longtime senator favorably, just 12% of Republicans – and 17% of unaffiliated voters – agree. Seventy-four percent (74%) of GOP voters have an unfavorable opinion of Specter, including 41% Very Unfavorable.

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Specter, who was first elected to the Senate in 1980, is seeking reelection in 2010 but faced a Republican primary challenge from former Congressman Pat Toomey. Specter has often taken positions on issues that angered his party’s more conservative base, most recently as one of only three Republicans who supported President Obama’s economic stimulus plan.

Because of the stimulus vote, 58% of Pennsylvania Republicans in February said they were less likely to vote for Specter next year.

Widely-reported Rasmussen polling in Pennsylvania last week showed Specter trailing Toomey by 21 points among Republican voters.

Specter, convinced he could win the general election but fearful he might lose his own party’s primary and not get that far, decided over the weekend to switch parties. Democratic leaders have reportedly assured him that he will not face a primary challenge on their side.

In 2004, Specter defeated Toomey by just two points in the Pennsylvania GOP Primary, but he then went on to win the general election by a 53% to 42% margin.

Sixty-eight percent (68%) of voters nationwide say they have followed news reports about Specter at least somewhat closely, with 34% saying they have followed Very Closely. Eleven percent (11%) say they haven’t followed news about the senator at all.

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