JEFFERSON CITY, Mo. (AP) — Michigan Republicans selected former Rep. Pete Hoekstra to take on Democratic Sen. Debbie Stabenow in November, while three GOP contenders were locked in a tight race Tuesday to oppose Democratic Sen. Claire McCaskill in Missouri.

In another closely watched Michigan primary, Democratic Rep. John Conyers staved off a primary challenge in a slightly redrawn district to advance to November’s election, when he will be strongly favored to win a 25th consecutive term in Congress.

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In the Missouri contest, Rep. Todd Akin of Missouri led former state treasurer Sarah Steelman and businessman John Brunner with about half the vote reported in Missouri. The winner and McCaskill will compete in what will be one of the most closely watched Senate races of 2012.

Hoekstra easily outpaced his nearest challenger, Clark Durant, overcoming a late push by Durant that included sharp attacks on his conservative record and cast him as a Washington insider.

Primary elections were being held in four states Tuesday. The Missouri race figured to have the greatest national significance: The GOP needs to net four seats from Democrats to gain control of the Senate and Republicans viewed McCaskill as among their top targets this year.

Other races included:

-Member- vs.-member primary contests in Michigan and Missouri, including a showdown between two of Missouri’s most prominent Democratic families. Reps. Russ Carnahan and William Lacy Clay vied for a St. Louis-area seat in a race brought on by congressional redistricting.

-A Democratic congressional primary for an open seat in Washington state.

-Republican primaries in Kansas could determine whether a conservative bloc would take control of the state Legislature.

In Missouri, all three Senate hopefuls have lambasted McCaskill for what they say are her close ties to President Barack Obama and, in particular, her vote for Obama’s signature health care law. The race took on a different dynamic in recent days as former Alaska Gov. Sarah Palin and former Arkansas Gov. Mike Huckabee – two of the GOP’s most prominent faces – lent their backing to candidates.

Palin, in particular, has been dogged in her support of Steelman, a former state treasurer. The 2008 Republican vice presidential nominee has appeared in television and radio ads and campaigned with Steelman at a series of events.

Steelman, 54, has said she hopes to capitalize on the momentum of Ted Cruz, the Republican nominee for the Senate in Texas. He rode strong tea party support – and a timely boost from Palin – to an upset victory in that state’s Senate primary last week.

Akin, 65, who drew Huckabee’s backing, has also billed himself as a tea party supporter and has a strong conservative voting record in Congress. But both Steelman and Brunner have sought to use that experience against him, portraying themselves as outsiders.

Brunner, 60, is a former CEO and chairman of Vi-Jon Inc., a health care products manufacturer. He has spent more than $7.5 million of his own money to campaign for the seat. He stops short of calling himself a tea party candidate, but he has the backing of FreedomWorks, a national tea party group that endorsed Cruz.

Polls indicate that any of the three would stand a good chance of defeating McCaskill. She took the unusual step of airing television ads targeting all three, a tactic that reflected the uncertain nature of the GOP primary.

In Michigan, Hoekstra will enter his race against Stabenow as the underdog. Stabenow, the chairwoman of the Senate’s agriculture committee, is seeking a third term and has enjoyed a steady lead in polls.

On the Democratic side in Michigan, Conyers held off a challenge from state Sen. Glenn Anderson. Conyers, who has had few serious primary challengers since first winning election in 1965, is expected to win the seat easily. Republican Harry Sawicki ran unopposed in the GOP primary.

In another Michigan race affected by redistricting, incumbent Democratic Reps. Hansen Clarke and Gary Peters were running against each other.

In Washington, seven people were running for a seat representing the newly drawn 1st Congressional District. They were Democrats Suzan DelBene, Darcy Burner, state Sen. Steve Hobbs, Laura Ruderman and Darshan Rauniyar; Republican John Koster; and independent Larry Ishmael. Washington state votes by mail, so all of the state’s 3.7 million voters received their ballots weeks ago. Voters had to have their ballots postmarked and in the mail by Tuesday or drop them off at special boxes around the state by 8 p.m. local time.

The Kansas primary was defined by a fight between the state GOP’s conservative wing and its more moderate elements. In early returns, eight moderate Republicans in the Kansas Senate were trailing. The incumbents who trailed included Senate President Steve Morris of Hugoton. A dozen moderate GOP senators were facing more conservative challengers.