Rudy Giuliani weighed in on the GOP primary for Wisconsin's U.S. Senate race Thursday, endorsing former Gov. Tommy Thompson.

Giuliani is the former mayor of New York City and really has no significant ties to Wisconsin. But he and Thompson have long been friends. Indeed, speaking at the Milwaukee Police Association Thursday, Giuliani called himself a "friend and admirer of Tommy Thompson for many years."

He also said that Thompson was one of "the best governors in America over the past 50 years. He's exactly what we need in Washington."

In October 2007, Thompson endorsed Giuliani in the GOP presidential primary. Thompson had also been in the field, but dropped out in August after finishing sixth in the Iowa straw poll. He was the first former presidential candidate to endorse in that race.

Thompson is running against Rep. Mark Neumann (R-Wis.), Wisconsin Assembly Speaker Jeff Fitzgerald (R) and businessman Eric Hovde in the Republican primary. The winner will face off against Rep. Tammy Baldwin (D-Wis.) in the general election.