In Missouri's Senate primary, there's a little something for every kind of conservative.

Today, Republicans in the Show Me State will pick a challenger for Democratic Sen. Claire McCaskill, and the dominant wings of the conservative movement can find niche appeal in the three GOP contestants: a tea partier endorsed by Sarah Palin, a businessman backed by the Chamber of Commerce, and a social conservative who's pursued the state's Christian voters.

Polls of varying credibility differ on who leads the three-way contest, but the last time opinion was measured by a polling firm considered reliable by ABC News, a St. Louis Post-Dispatch survey conducted by Mason-Dixon July 23-25 showed St. Louis businessman John Brunner in a six-percentage-point lead.

Pro-business Republicans have Brunner, who has largely self-funded his campaign, pouring in nearly $7 million of his own money and outspending his competitors $6.8 million to their combined total of $3.8 million. The U.S. Chamber of Commerce, which sided against the tea party in backing Indiana Sen. Dick Lugar over his successful challenger Richard Mourdock, has spent money to support Brunner.

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Fiscal tea partiers have Sarah Steelman, the former state treasurer who is backed by Sarah Palin and the national group Tea Party Express, which lends its stamp of approval (and some independent spending) to fiscally conservative candidates. Palin recorded a TV ad for Steelman and campaigned with her outside Kansas City on Friday. The ad, in which Palin calls Steelman a "mama grizzly," is ubiquitous on airwaves in the state.

And for Missouri's social-issue voters, there's Rep. Todd Akin, a Christian conservative from St. Louis who served in the U.S. Navy and since 2001 has represented a congressional district that stretches from St. Louis's suburbs to rural areas northwest of the city. Akin holds a divinity degree from Covenant Theological Seminary in St. Louis, and he recently aired this TV ad exhorting Missouri Republicans to vote on Tuesday as an exercise of America's religious founding.

Each would make the Senate more conservative in his or her own way, but it's clear who McCaskill would rather face: Since last month, McCaskill has been running ads attacking all three of her potential challengers, but the ad purportedly hitting Akin seems designed to boost his credibility among GOP primary voters, patting him on the back as "the most conservative congressman in Missouri," a "crusader against bigger government" with a "pro-family agenda."

All three polled ahead of McCaskill when Mason-Dixon asked about potential general-election matchups, but Brunner performed the best, beating McCaskill by 11 percentage points. Steelman topped McCaskill by eight percentage points, and Akin edged the incumbent by five percentage points.