Three conservatives face off in the Republican Senate primary in Missouri

It's decision time for wealthy businessman John Brunner, Rep. Todd Akin and former state treasurer Sarah Steelman on Tuesday as the three Republicans face off in Missouri's U.S. Senate primary.

Unlike recent elections such as the Senate primary in Texas, there isn't a clear tea-party-backed candidate in this race: Each politician is claiming some tea party support and boasting conservative credentials.

It's a mixed bag when it comes to right-leaning endorsements. Former Alaska Gov. Sarah Palin and the Tea Party Express have thrown their weight behind Steelman, while FreedomWorks and Wisconsin Sen. Ron Johnson as well as Oklahoma Sen. Tom Coburn are supporting Brunner. Meanwhile, Rep. Michele Bachmann as well as former Arkansas Gov. Mike Huckabee are endorsing Akin.

The top three candidates spent this past weekend and Monday making last-minute pitches to Missouri voters, who are tasked with choosing a Republican nominee to face Democratic Sen. Claire McCaskill this fall.

"Together, we'll get America working again," Brunner told supporters in a video message publicized through Facebook Monday. "We have more Facebook friends than these careers politicians. That's what going to make a difference--a citizen senator in Washington DC."

Akin continued to define himself as the "proven conservative" in the race, while Steelman touted her outsider status.

All three candidates have balanced waging a strong primary campaign with a longer-term strategy of focusing on the general election against McCaskill--whom national Republicans have marked as one of their top Senate takeover targets this year.

McCaskill trailed each of the three top Republican candidates in a Mason-Dixon poll taken in late July. The Missouri senator has already received in-person support from Vice President Joe Biden, as both parties have marked the race as a top priority.

Obama lost Missouri in 2008 by less than 4,000 votes, but this cycle both parties regard Missouri as Mitt Romney territory rather than a swing state.

Missouri has an open primary system, meaning that any registered state voter can participate in the party primary of his or her choosing Tuesday. McCaskill faces no opposition.

In other primary activity taking place on Tuesday, voters in Kansas, Michigan and Washington head to the polls.

In Michigan, former Republican Rep. Pete Hoekstra faces tea partier and former Reagan official Clark Durant in the race to take on Democratic Sen. Debbie Stabenow.