Redistricting brought on member-on-member primaries Tuesday in Arizona and party tilts to nominate candidates to replace a retiring Oklahoma congressman.
Flake led real estate investor Cardon 70 percent to 21 percent with 33 percent of precinct reporting, AZCentral.com reported late Tuesday.
The race to watch was in Arizona's 6th Congressional District, pitting two freshman Republicans against each other, Roll Call reported. The results appeared to be a tossup late Tuesday.
The campaign between GOP Reps. Ben Quayle, the son of former Vice President Dan Quayle, and David Schweikert took a personal turn because both have solid conservative voting records, observers said. Most unaligned operatives say they think Schweikert will win, but one national Republican handicapper warned that Quayle has an organization adroit at getting out the vote.
The winner of the Flake-Cardon contest will face presumptive Democratic nominee, former Surgeon General Richard Carmona, in the fall.
Rep. Paul Gosar, a Republican, moved from the competitive 1st Congressional District to the newly drawn 4th Congressional District, which Roll Call classified as a Safe Republican seat.
A three-way race turned into a two-way race between Gosar and state Sen. Ron Gould when scandal swamped Pinal County Sheriff Paul Babeu. Both Gosar and Gould predicted victory and both have allies that can help them, Roll Call said.
Former Rep. Matt Salmon, making a congressional bid after a 12-year hiatus, is expected to win the GOP primary in Arizona's 5th Congressional District. His rival, former state Speaker Kirk Adams, has a number of endorsements, including 2008 vice presidential nominee Sarah Palin, who traveled to Arizona to campaign for Adams Monday, Roll Call said.
The Arizona 9th Congressional District has been handicapped as a tossup by analysts.
The Democratic field is crowded -- former state Sen. Kyrsten Sinema, former state party Chairman Andrei Cherny and state Sen. David Schapira are seeking the party's nomination.
In the Republican contest, former Paradise Valley Mayor Vernon Parker, ex-Chandler City Councilman Martin Sepulveda, businessman Travis Grantham and retired Air Force officer Wendy Rogers are candidates.
In Oklahoma's 2nd district, former District Attorney Rob Wallace won the Democratic runoff, The Oklahoman reported. Wallace had 57 percent of the vote to 43 percent for seed company owner Wayne Herriman.
On the Republican side, plumbing company owner Markwayne Mullin defeated state Rep. George Faught, also by 57 percent to 43 percent.
Wallace and Mullin will face each other to replace retiring Rep. Dan Boren. Roll Call rated this race as leaning Republican.