Former Gov. Tommy Thompson leads three other candidates in the race for the Republican nomination for the US Senate seat open in Wisconsin this year, according to results of the Marquette Law School Poll released on Wednesday. Thompson also drew more support than Democratic candidate Tammy Baldwin in a head-to-head trail heat.

But a quarter of people who said they plan to vote in the Aug. 14 Republican primary said they were undecided or didn’t know whom they would support, indicating that there is potential for substantial change before the election.

Among people who said they intended to vote in the Republican primary, 34% said they backed Thompson, with 16% supporting former Congressman Mark Neumann, 14% for Madison businessman Eric Hovde, and 10% for Assembly Speaker Jeff Fitzgerald.

In a Thompson-Baldwin match, Thompson was the choice of 49% of people in the poll, with Baldwin, a Democratic member of Congress from Madison, drawing 41%. In other head-to-head matches, Baldwin and Neumann tied at 44% each, and Baldwin led both Fitzgerald (45% to 39%) and Hovde (45% to 36%).

In an “On the Issues with Mike Gousha” session at Eckstein Hall, Charles Franklin, director of the Marquette Law School Poll, said that if it hadn’t been for the recall election for governor on June 5, the Senate race would have been one of the most fascinating elections in recent state politics. But the race drew little attention until now.

In another poll result, Democratic President Barack Obama was supported by 49% of likely voters in the November election, with Republican candidate Mitt Romney supported by 43%. In late May, the poll found Obama ahead 51% to 43%.

Full results of the poll may be found by clicking here. The conversation about poll results between Gousha, the Law School’s distinguished fellow in law and public policy, and Franklin, visiting professor in law and public policy, may be found by clicking here.