WASHINGTON - North Carolina House Speaker Thom Tillis on Tuesday captured the nomination to oppose imperiled Democratic Sen. Kay Hagan, overcoming antiestablishment rivals by a comfortable margin in the first of a springtime spate of primaries testing the strength of a tea party movement that first rocked the Republican party four years ago.

In Ohio, Cuyahoga County Executive Ed FitzGerald won the Democratic nomination to challenge Gov. John Kasich in the fall, while House Speaker John A. Boehner rolled to renomination for another term in Congress, his 13th.

On a night that was kind to Republican incumbents, Rep. Susan Brooks of Indiana easily fended off a challenge from the right, rolling up 75 percent of the votes in a three-way race. First-term Rep. David Joyce of Ohio had a slightly tougher time but was running well ahead of his tea party rival.

In North Carolina, Tillis was winning about 48 percent of the vote with ballots counted in 46 percent of the state's precincts. He needed 40 percent to avoid a July runoff. Greg Brannon was running second and Mark Harris third.

Also in North Carolina, former American Idol runner-up Clay Aiken seized a narrow lead as he sought the Democratic nomination to oppose Republican Rep. Renee Ellmers in the fall. A Democratic runoff was possible.

Elsewhere in the state, Rep. Walter Jones, an antiwar Republican, was running ahead of his challenger.

Hagan, whom Republicans have made a top target in their drive to win a Senate majority in the fall, won renomination with about 80 percent of the primary vote over a pair of rivals.

Tuesday marked the beginning of the political primary season in earnest, and over the next several months Republicans will hold numerous contests featuring incumbents or other establishment figures against tea party challengers. Some of the races are in states where the identity of the party's candidate might mean the difference between victory and defeat this fall, such as Alaska, Georgia, Iowa, and Kentucky. In other areas, it will matter less, with the party strong no matter who wins, including in Kansas, Mississippi, Nebraska, Oklahoma, and South Carolina.

Tillis ran with the support of the U.S. Chamber of Commerce, the National Right to Life Committee, and former presidential candidate Mitt Romney. Brannon, an obstetrician, had the backing of Sen. Rand Paul of Kentucky, a tea party favorite. Harris, a Baptist pastor, countered with former Arkansas Gov. Mike Huckabee, whose popularity with evangelical voters briefly made him a force in the race for the 2008 presidential nomination.

Establishment figures made little or no secret of their desire for Tillis to prevail, fearful that any other challenger to Hagan could mean a replay of 2010 and 2012, when Republicans lost winnable Senate races in Nevada, Indiana, and Missouri.

"You can't defeat Kay Hagan with a factionalized" party, Tillis said.