There's more than his recent bus tour, which included a fender bender with a tree, to suggest that Wisconsin Gov. Scott McCallum is in for one bumpy ride in the race to keep his job.

The Republican incumbent has served less than two years in office, succeeding perhaps the most popular politician in state history, former four-term Gov. Tommy Thompson, who quit the governorship to join the Bush Administration as the Secretary of Health and Human Services last year.

"It's been the first time we've really had a real contest since 1986, which is when Thompson first won," said Ken Mayer, a political science professor at the University of Wisconsin.

But even in his absence, Thompson is a significant factor in this election. He helped bring President Bush to Wisconsin to campaign for McCallum, and Thursday traveled to the state to give the governor a $2.7 million check to help pay for low-income energy costs during the hotter than normal summer.

Thompson has also unintentionally boosted the name recognition of the Libertarian candidate for the seat -- his brother Ed, a bar owner and former small town mayor.

"Tommy's a career politician and I'm a career common guy," said Ed Thompson, who enjoys no political backing from his brother.

Although he has raised more money than any third party candidate in Wisconsin history, polls suggest Ed Thompson -- at 10 percent -- might be nothing more than a spoiler.

The same polls show McCallum with little more than a 50 percent approval rating and in a dogfight with Democrats in the race -- Milwaukee Rep. Tom Barrett, Attorney General Jim Doyle and Dane County executive Kathleen Falk. The three face off in September's Democratic primary to see who will get the job of trying to topple McCallum in November's general election.

"The key question for the Democrats is who has the best chance of beating him and each of the candidates is trying to make that point," Mayer said.

McCallum has been slammed by Democrats for overseeing a state budget that went from a surplus to being more than $1 billion in the hole.

They say the state's future would be brighter without McCallum as governor.

"We simply cannot continue to hold this state government together with duct tape and bubble gum," said the five-termer Barrett.

McCallum casts the complaints aside, saying he's more concerned about the future and that should he return to office, he will work to trim state spending.

"It's really the sniping and the criticism versus here is where we are going as a state," he said.

His own spending is a different story in this wide-open campaign. With more than $5 million in the bank, McCallum has raised more money than any of his competitors.

It's a sum that just might be decisive enough to smooth the bumps McCallum already faces.

Fox News' Jeff Goldblatt contributed to this report.