PORTLAND — Gov. John Kitzhaber and Dennis Richardson easily won their respective primaries, setting up a fall gubernatorial race in which the state’s health-insurance-exchange plan, Cover Oregon, figures to be a key issue.

Monica Wehby, a physician, won the Republican nomination to oppose Democratic Sen. Jeff Merkley in a race that GOP strategists hope can become more competitive as the year unfolds.

On a day when five other states — Kentucky, Arkansas, Georgia, Idaho and Pennsylvania — held primaries, Richardson, a state representative from southern Oregon, had more than 60 percent of the vote Tuesday and all his opponents were struggling to reach double-digits.

Kitzhaber’s only registered rival, a political unknown from Salem, failed to follow through with a campaign.

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Democrats enjoy a sizable advantage in voter registration in Oregon and Republicans haven’t won a statewide race since 2002, but the failed rollout of Cover Oregon gives Richardson an opportunity in a state that hasn’t elected a Republican governor since 1982.

Voters in Jackson County in southern Oregon voted to ban genetically engineered crops by a 2-to-1 ratio. A similar measure enjoyed a strong lead in neighboring Josephine County. A pair of competing campaigns raised $1.3 million to sway Jackson County’s 120,000 registered voters.

In other races:

Georgia: In a boost to Democrats, Republicans seeking Georgia’s Republican U.S. Senate nomination will be forced into a July 22 runoff after no candidate topped the 50 percent vote mark in today’s primary.

David Perdue, a former chief executive officer of Dollar General and Reebok, and Rep. Jack Kingston will compete in the runoff for the right to run against Democrat Michelle Nunn in November for an open seat. Nunn, the daughter of former Democratic U.S. Sen. Sam Nunn of the Georgia, easily won her party’s nomination against three opponents.

The two Republicans will spend the next eight weeks competing against each other in what promises to be a tough and expensive campaign, instead of focusing their fire on Nunn, 47.

Along with Perdue, Kingston and Secretary of State Karen Handel, Reps. Phil Gingrey and Paul Broun also were on the ballot, and the race was fiercely expensive — $10 million had been spent on TV commercials through the end of last week.

Kentucky: Senate Republican leader Mitch McConnell easily survived a tea-party challenge Tuesday as voters in Kentucky and five other states went to the polls on the biggest primary day of 2014 so far.

McConnell coasted to victory over Louisville businessman Matt Bevin in Kentucky’s Republican U.S. Senate primary. With 97 percent of precincts reporting, McConnell had 60 percent to Bevin’s 35.7 percent.

He now faces a more daunting test as the general- election campaign begins. Alison Lundergan Grimes, who handily won the nomination in the state’s Democratic primary, is running even with the five-term Senate veteran in the polls as she seeks to unseat a major leader of Congress, something that’s been done only three times in the past 20 years.

Idaho: Rep. Mike Simpson prevailed in the Republican primary for Idaho’s 2nd Congressional District on Tuesday, fending off a conservative challenger who drew early support from anti-tax advocates. Simpson will face Democrat Richard Stallings in November. Stallings, a former four-term congressman from Idaho, ran unopposed.

Pennsylvania: Democrats took the spotlight in Pennsylvania, where voters soundly rejected a longtime congresswoman’s bid for the gubernatorial nomination to challenge Republican incumbent Tom Corbett. Businessman Tom Wolf crushed Rep. Allyson Schwartz after he flooded the state with ads stressing his independence from Washington.

Chelsea Clinton’s mother-in-law, former Rep. Marjorie Margolies, lost her bid to return to the House — despite fundraising and other campaign help from Bill and Hillary Rodham Clinton. Margolies served one term in the early 1990s, and the Clintons had boosted her campaign this time.

Arkansas: Sen. Mark Pryor, a Democrat, faces a tough fight to hold his seat against Republican Rep. Tom Cotton. Both were unopposed Tuesday. Voters selected two former congressmen — Democrat Mike Ross and Republican Asa Hutchinson — to vie to replace the term-limited Democratic Gov. Mike Beebe.

Seattle Times news services