Mississippi's Senate primary race on Tuesday represented the ultraconservative tea party's last, best chance to topple a Republican establishment-backed candidate in this year's midterm elections, and prove it remains relevant a few years after it burst upon the political scene.
Nominations for the Senate are also on the ballot in Alabama, Iowa, Montana, New Jersey, New Mexico, and South Dakota in a year in which Republicans need to gain six seats to win a majority. Five states picked nominees for governor, including California, where Democrat Jerry Brown cruised to renomination to a fourth term.
A loose coalition of small-government, anti-tax activists, the tea party rose to prominence in the wake of President Barack Obama's election 2008 and forced the Republican party further to the right than many Americans were comfortable with.
After a string of victories in midterm elections sent tea party candidates to the House and Senate, some of their luster has faded.
Many establishment Republicans fear tea party victories in primaries only play into Democratic hands as their candidates are often too right-wing for general elections voters.
The eight states holding primaries will help determine whether Republicans have a credible chance of gaining the six Senate seats required to take control of the chamber in November elections.
The Republicans are virtually certain to retain their House majority, and control of the Senate would allow them to shut down Obama's legislative agenda during the last two years of his term. For this reason, the Republican establishment is working hard to keep tea party candidates off the ballot in November.
In southern Mississippi, six-term Sen. Thad Cochran is facing conservative challenger Chris McDaniel, who carries the hopes of tea party supporters nationwide, eager to topple a high-profile Republican incumbent after earlier losses in Senate primaries in Texas, North Carolina, and Kentucky.
Returns from 91 percent of the state's precincts showed the challenger narrowly ahead in a three-way race, and a June 24 runoff was increasingly possible if neither candidate gains more than 50 percent of the vote.
During the campaign, Senator Cochran, 76, emphasized the federal money that he has steered to Mississippi for decades. The 41-year-old Mr. McDaniel's critique of the incumbent is that he's too willing to go along with Democrats in Washington.
McDaniel's campaign suffered a setback when four of his supporters were arrested on charges of photographing Cochran's bedridden wife, who has dementia.
McDaniel said he knew nothing about it, but Cochran supporters suspected dirty politics.
Cochran meanwhile has campaigned with Southern gentility, the party establishment's support and a promise to leverage his Senate seniority for federal help for the state. He cast himself as a reliable opponent of Obama.
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 Republicanprimary will be the heavy favorite in November against the Democratic nominee.
One race, which may affect control of the Senate is in Iowa, where Democratic Sen. Tom Harkin's retirement triggered a feisty Republican primary.
State Sen. Joni Ernst beat out four other challengers Tuesday, following a campaign whose ads about guns and hog castration helped her shore up support among conservatives. Republicans are eyeing as a prime opportunity to pick up a seat.
In North Dakota, former Gov. Mike Rounds cruised to victory in the Republican primary for the US Senate seat being vacated by retiring Democratic Sen. Tim Johnson. Republicans believe South Dakota presents one of their best chances nationally to take a seat from Democrats.
Associated Press writer Tom Beaumont in Iowa contributed to this report.
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