TOP OF THE TICKET

On a day with primary elections in eight states, the marquee race in Mississippi, where six-term GOP Sen. Thad Cochran faced his toughest re-election fight ever, remained too close to call hours after the polls closed. The state's Republican establishment backed Cochran against state Sen. Chris McDaniel, a favorite of the tea party.

Voters also chose nominees in Alabama, California, Iowa, Montana, New Jersey, New Mexico and South Dakota.

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MISSISSIPPI TURNING?

The closing days of the Cochran-McDaniel race were dominated by a controversy involving, of all things, a camera in a nursing home. Four McDaniel supporters were arrested on charges tied to the surreptitious photographing of Cochran's bedridden wife, who has dementia.

McDaniel said he knew nothing about it, but Cochran supporters suspected dirty politics.

Cochran, 76, emphasized the federal money — sometimes called pork — that he has steered to Mississippi for decades. The 41-year-old McDaniel's critique of the incumbent was that he's too willing to go along with Democrats in Washington.

While a McDaniel win would be a rare victory for tea party conservatives this year over a candidate favored by the party's establishment wing, it's not likely to affect control of the Senate. The winner of the GOP primary will be the heavy favorite in November against the Democratic nominee, former U.S. Rep. Travis Childers.

The Cochran-McDaniel showdown produced record spending in the relatively small state. Third-party groups spent about $8.4 million, mostly for TV ads.

That's on top of $3 million spent by Cochran's campaign and $1 million from McDaniel's. The total outlay amounts to $4.13 for each of Mississippi's 3 million residents, and $6.53 for each of its 1.9 million registered voters. The cost-per-vote figure promises to be much higher, given that primaries usually draw only a fraction of eligible voters.

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SQUEALING PIGS IN IOWA

Democratic Sen. Tom Harkin's retirement triggered a feisty Republican primary in Iowa, where state Sen. Joni Ernst made national news with a TV ad boasting that she castrated hogs as a farm girl. (She will "cut the pork" in Washington ... get it?) Ernst went on to win endorsements from Sarah Palin, Mitt Romney and others.

The goofy nature of the ad doesn't really reflect Ernst's personality, but the attention it generated made her the star in a then-muddled field of five. She won the nomination, defeating businessman Mark Jacobs.

She will face U.S. Rep. Bruce Braley, who was unopposed for the Democratic nod.

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CALIFORNIA'S TOP TWO TAKE ALL

California holds its primaries under its unusual all-candidates system, in which the top two finishers, regardless of party, face off in November.

Democratic Gov. Jerry Brown grabbed one spot in the gubernatorial race. Two Republican candidates, former investment banker Neel Kashkari and state legislator Tim Donnelly, were locked in a fight for second place. Donnelly, the more ardently conservative of the two, has compared President Barack Obama to Adolf Hitler.

Seven-term U.S. Rep. Mike Honda is being challenged by fellow Democrat Ro Khanna, a patent lawyer backed by several high-tech interests.

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BIG NAMES, LITTLE SUSPENSE IN SOUTH DAKOTA AND MONTANA

Republicans see South Dakota and Montana as prime opportunities to take Senate seats from Democrats this year. The showdowns will occur in November, with nominees becoming official on Tuesday.

Former South Dakota Gov. Mike Rounds won the GOP Senate nomination for the seat being vacated by Democrat Tim Johnson. Businessman Rick Weiland was unopposed as the Democrats' pick.

In Montana, then-Lt. Gov. John Walsh was appointed in February to the Senate seat that fellow Democrat Max Baucus left to become ambassador to China. Walsh is trying to win a full six-year term, and will face U.S. Rep. Steve Daines.

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UP NEXT

The next primaries are scheduled for June 10 in Maine, Nevada, North Dakota, South Carolina and Virginia, with a runoff in Arkansas.

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Associated Press writer Bill Barrow in Georgia contributed to this report.