Wisconsin's Senate race is a pure toss-up if longtime Gov. Tommy Thompson (R) or former Rep. Mark Neumann (R-Wis.) wins the GOP primary, according to a new poll from the Democratic-leaning Public Policy Polling.

Thompson leads Rep. Tammy Baldwin (D-Wis.) by 47 percent to 45, while Baldwin leads Neumann by 46 percent to 45, according to the poll.

The poll applies a "likely voter" model that is unusual this early in the election because it also polled the upcoming Wisconsin gubernatorial recall race. This might slightly distort the numbers, since only those likely to vote in the gubernatorial race are polled here, but it is mostly in line with other polls of the race.

Thompson has led his GOP opponents in previous primary polls, and because of his sky-high name recognition in the state and relatively centrist record he appears to be the strongest candidate. But Neumann's close numbers in this poll suggest that, at least at this point, if the hardline conservative is nominated he'll have a good chance in the general election.