WASHINGTON -- Six-term Republican Sen. Thad Cochran and tea party-backed challenger Chris McDaniel collided in Mississippi on Tuesday in a ferocious battle between insurgents and the establishment in a party divided along ideological lines. On the busiest night of the primary season, Democratic Gov. Jerry Brown of California sought nomination to a fourth term.
Primary elections for the Senate spread from Alabama to New Jersey, Montana, New Mexico, South Dakota and Mississippi -- and to Iowa, where Republican state Sen. Jodi Ernst battled four rivals for the right to oppose Rep. Bruce Braley in the fall for a seat long in Democratic hands.
The first few ballots counted in Mississippi favored Cochran, with McDaniel close behind.
In Alabama, Republican Sen. Jeff Sessions was nominated to a new term without opposition, and Republican Gov. Robert Bentley overwhelmed what little competition he had.
Apart from California, there were gubernatorial primaries in Iowa, New Mexico, and South Dakota, both states where Republicans sought new terms and Democrats were picking candidates to challenge them.
Dozens of nomination races for House seats dotted the ballot, too, including 38 in California's open primary system, which awarded spots on the November ballot to the two top vote-getters regardless of party.
The Senate contest between Cochran and McDaniel in Mississippi drew top billing, a heated race between a 76-year-old pillar of the GOP establishment who has helped funnel millions of dollars to his state and a younger state lawmaker who drew backing from tea party groups and former Republican vice presidential candidate Sarah Palin. The campaign took a turn toward the sensational when four men, all McDaniel supporters, were arrested and charged with surreptitiously taking photographs of the senator's 72-year-old wife, who suffers from dementia and has long lived in a nursing home.
Cochran's supporters advertised in at least one black newspaper in the race's final days as they appealed to traditionally Democratic voters to extend his career.
Vicksburg Mayor George Flaggs, a black Democrat who served for 26 years in the state Legislature, said he was supporting the white, Republican incumbent. He said the senator has secured federal funding for a U.S. Army Corps of Engineers research station in his city, adding, "It is incumbent for me to vote for Thad."
State law required the primary leader to gain at least 50 percent of the vote to win the nomination outright. The presence of a third Republican on the ballot, Thomas Carey, raised the possibility that a June 24 runoff between the top two finishers would be needed.
The race was arguably the year's last good chance for the tea party wing of the party to topple an establishment favorite in a Senate primary, following losses in Texas, North Carolina, Georgia and Kentucky.
The impact of the race seemed less in the national battle for control of the Senate, where Republicans need to gain six seats this fall to capture a majority. Former Rep. Travis Childers and three others sought the Democratic nomination to oppose the winner of the Cochran-McDaniel race in Mississippi, a state that last elected a Democratic senator in 1982.
The national stakes were clearer in Iowa, where Democratic Sen. Tom Harkin's retirement created an open seat that Democrat Braley, a fourth-term lawmaker, sought to fill, as did Ernst and three rival Republicans.
Ernst fashioned her rise in the race on memorable television commercials.
"I grew up on an Iowa farm castrating hogs, so when I get to Washington, I'll know how to cut pork," she said in one of them, concluding with a smile, "Let's make 'em squeal." She was able to transcend many of the intra-party divisions that flared in other races, gathering support from Palin and former Sen. Rick Santorum as well as Mitt Romney, the party's 2012 presidential candidate.
Her rivals on Tuesday's ballot included Mark Jacobs, the former CEO of Reliant Energy; former U.S Attorney Matt Whitaker; businessman Scott Schaben and Sam Clovis, a college professor. A state convention will be required to select a nominee if none of the primary contenders gains at least 35 percent of the vote.
In other Senate races, appointed Democratic Sen. John Walsh and Republican Rep. Steve Daines in Montana each faced a pair of primary rivals en route to a likely race in the fall that the GOP is expected to target as an opportunity to gain a seat.
Republicans eyed another fall pickup opportunity in South Dakota, where Democratic Sen. Tim Johnson has chosen to retire. Former Gov. Mike Rounds and three other Republicans sought their party's nomination. Rick Weiland, making his third try for a seat in Congress, was unopposed by other Democrats.
Sen. Cory Booker, D-N.J., had no competition for renomination, and four Republicans sought to oppose him in the fall.
In New Mexico, two Republicans, former state party chairman Allen Weh and attorney David Clements, vied for the nomination to oppose Democratic Sen. Tom Udall.
Democrats fielded no candidates in Alabama to oppose Sen. Jeff Sessions, who faced no primary competition either.
California's open primary law produced a crowded ballot, with three-term incumbent Gov. Brown and 14 others competing for primary votes. Republicans included Neel Kashkari, a former Treasury Department official, and Tim Donnelly, a state assemblyman and conservative favorite.
In Iowa, five-term Gov. Terry Branstad drew a challenge in the Republican primary. State Sen. Jack Hatch was unopposed for the Democratic nomination.
South Dakota Gov. Dennis Daugaard faced primary opposition from state Rep. Lora Hubbel. Democrats chose between state Rep. Susan Wismer and Joe Lowe, a former state agency head.
First-term Gov. Susana Martinez in New Mexico was unopposed for re-nomination. Five Democrats sought the right to oppose her in the fall.
In Alabama, former Rep. Parker Griffith and Kevin Bass, a former minor league baseball player, ran for the Democratic gubernatorial nomination, the winner to oppose Republican Gov. Bentley in the fall.
New voter identification laws were in effect in Mississippi and Alabama, although there were no difficulties immediately reported.