Even after abortion opponents became a strong force within the Kansas GOP in the 1990s, moderate Republicans prevented them from imposing as many restrictions on providers as they wanted. When conservatives on the State Board of Education pushed Kansas toward repudiating evolution in science standards for public schools, they inspired a backlash.
Ed Flentje, a professor of public administration at Wichita State University, notes social conservatives have been a force in Republican politics since prohibition was an issue.
They've been wedded within the GOP to low-tax, small government conservatives for decades. Threats from strong Democrats push the coalition to the center, said Flentje, co-author of a new book about Kansas politics.
"What if Sebelius were back here running for the seat?" he said of the Senate race.
Meanwhile, policy differences between Tiahrt and Moran sometimes seem subtle.
Moran voted consistently against all proposed versions of President Bush's No Child Left Behind education reform law in 2001; Tiahrt supported a House GOP version but not the final version. Tiahrt strongly opposes Obama's policies but voted once for money for the "cash for clunkers" program, which Moran opposed.
The American Conservative Union gives Tiahrt a lifetime rating of more than 95 percent; Moran's score is almost 92 percent. The U.S. Chamber of Commerce gives Tiahrt a career score of 94, while Moran's is 91.
"We're still in the Reagan era," Flentje said. "Most folks think the voters in the primary are going to be those passionate folks who push the party to the extremes."