Kansas Republicans were deciding Tuesday which of two veteran congressmen would be the most aggressive conservative champion in the U.S. Senate against President Barack Obama and his fellow Democrats.

The GOP primary race between Reps. Jerry Moran and Todd Tiahrt is the hottest political contest of the year in Kansas — and among the nastiest in the past generation. Both candidates have run hard to the right.

Republicans also were winnowing crowded primary fields for the House seats Moran and Tiahrt are giving up, as well as the one held by retiring Democratic Rep. Dennis Moore. They expected to name U.S. Sen. Sam Brownback their nominee for governor over token opposition and were settling a three-way race for Kansas secretary of state.

Democrats were picking nominees for three House seats and deciding whether Secretary of State Chris Biggs would get a chance to keep the office. They also were selecting a Senate nominee, though none of the five hopefuls was given much of a chance to win in November.

Biggs predicted that 19 percent of the state’s 1.7 million voters, or about 324,000, would participate in the primary.

The decision by Brownback, a conservative Republican, to run for governor set up the contentious race for his Senate seat.

Moran hoped a huge majority in his home congressional district, the sprawling 1st of western and central Kansas, would push him to victory. He’s held the seat since 1997.

“I expect Republican turnout to be high,” Moran said after a Monday pep talk to supporters at his Topeka campaign office. “The interest is intense.”

Moran exuded confidence, and his aides described him has having a solid lead. But Tiahrt is confident abortion opponents and other conservative activists will come out for him.

Tiahrt has represented the 4th District of south-central Kansas since 1995. Both he and Moran have strong anti-abortion voting records in Kansas, but Tiahrt has closer ties to the anti-abortion group Kansans for Life. His wife, Vicki, has served on its board.

“What I put faith in is the volunteers that are out there holding signs at sign-waves, knocking on doors,” Tiahrt said during a telephone interview.

Tiahrt has tried to raise doubts about Moran’s commitment to being a conservative, partly by pointing to a dozen tax votes by him, some stretching back to Moran’s days as a state senator in the early 1990s. Moran has suggested Tiahrt went Washington, noting Tiahrt’s family lives in the area.

Moran has touted endorsements by conservative senators such as Jim DeMint of South Carolina and Tom Coburn of Oklahoma. But Tiahrt had the backing of former GOP vice presidential nominee Sarah Palin.

Two other minor GOP candidates were on the ballot.

The Democrats’ field included state Sen. David Haley, of Kansas City; Lisa Johnston, a Baker University administrator; and Charles Schollenberger, a former newspaper editor and reporter from Prairie Village.

The GOP nominee will be heavily favored to win because Kansas hasn’t elected a Democrat to the Senate since 1932.

The secretary of state’s race was notable because the Republican contest included Kris Kobach, a law professor who helped write Arizona’s anti-immigration law. On the Democratic side, Biggs faced state Sen. Chris Steineger, of Kansas City.

The only challenge to Insurance Commissioner Sandy Praeger’s re-election was in the GOP primary, where she faced a tea party candidate, David Powell, of El Dorado.

The race to succeed Moran in the 1st Congressional District had six GOP candidates, and five Republicans were running for Tiahrt’s seat in the fourth.

Democrats expected state Rep. Raj Goyle, of Wichita, to emerge from a 4th District primary contest; former Salina Mayor Alan Jilka is the only Democrat in the 1st.

Nine GOP candidates were on the ballot in the 3rd District, centered on the Kansas City area, where Moore is retiring. His wife, Stephene, had a Democratic primary challenger but was expected to win easily.

In the 2nd District of eastern Kansas, GOP leaders expected incumbent Republican Lynn Jenkins, of Topeka to turn back a primary challenge from state Sen. Dennis Pyle, of Hiawatha. Three Democrats were running.