(Scott Olson/Getty Images)

ABC News' Shushannah Walshe and Kyle Blaine report:

Today more Americans are able to vote than any other day this primary season, in fact this amount of voters won't go to the polls until November. Eight states are voting today including Mississippi, Iowa, California, New Jersey, South Dakota, Montana, Alabama, and New Mexico.

WHO'S ON THE BALLOT? Today's marquee race is another tea party vs. establishment battle that could mean the end of a six-term senator. Another senate race features a gun toting, hog castrating candidate who is trying to beat four of her Republican opponents and avoid a nominating convention. California is trying out what is called a jungle primary for the first time in a statewide election. And there's even a spiritual guru with the backing of Kim Kardashian on the ballot in that state. That's just a sample of the many candidates voters have in the eight states voting today.

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DIRTY SOUTH: Incumbent Sen. Thad Cochran is in the fight of his life against tea party challenger state Sen. Chris McDaniel in the Mississippi GOP Senate primary. This has been called the dirtiest primarythis year and is the marquee race today. WHY IT MATTERS: Cochran, known as "Gentleman Thad," was elected to the House in 1972, serving three terms before being elected to the Senate and he could very well fall to the tea party today. It has been an increasingly nasty-and at times bizarre-race. Last month a supporter of McDaniel's snuck into a nursing home where Cochran's bedridden wife has lived for over a decade with dementia and secretly filmed her. He put the video online causing a firestorm that has dominated the headlines through today. McDaniel has said he has no relationship with the right wing blogger and was not involved in the decision to sneak into Rose Cochran's room. The blogger was arrested, as well as three others including a tea party leader. Cochran has been vocal about his disgust over the incident and he used it in a campaign ad decrying "dirty politics." McDaniel has some big-name backers including Sarah Palin and Rick Santorum and they have both have appeared in ads for him. They all have joined with McDaniel to stress his call that Cochran embodies Washington, D.C. and his time is over. Third party money has poured into the state making this one of the most expensive primaries this cycle. Cochran is backed by former Mississippi Gov. Haley Barbour and former Mississippi Sen. Trent Lott, also backed him and lent his voice to a radio ad. In a statement released Monday by the pro-Cochran, Barbour-backed Mississippi Conservatives PAC, Barbour called Palin and Santorum "outside celebrities" only involved in the race "to politically help themselves nationally, not because they are trying to help (Mississippi.)" The winner tonight is the likely victor in this red state.

AND SHE RIDES A HARLEY TOO: Hog-castrating Iowa state senator and Iraq War veteran Joni Ernsthas risen from the pack of Republican hopefuls in the Iowa GOP senate primary, including her closest contender, former energy executive Mark Jacobs, who has thrown a considerable amount of his own money into the race. Rick Perry supported attorney Matt Whitaker, Rick Santorum backed radio host Sam Clovis and car salesman Scott Schaben round out the pack of candidates vying for the nomination in Tuesday's primary. WHY IT MATTERS: Nabbing an open Senate seat, especially one that belonged to a Democratic stalwart like Tom Harkin, is a top priority for the Republican Party as they try to edge Democrats out of the Senate majority. All the more reason having a clear cut winner Tuesday is important if they hope to beat the unopposed Democratic nominee Rep. Bruce Braley come November. If none of the five candidates past the 35 percent threshold in Tuesday's primary, then the winner will be decided at a nominating convention, which will be brokered by a small group of committed Republican delegates on June 14. Ernst's ascendance in the race-in large part due to a provocative adin which she compares castrating pigs on an Iowa farm to cutting pork in Washington-may diminish this possibility. A Des Moines Register poll from Sunday places her at the top of the heap with 36 percent of the vote, just one percent over the required 35 percent to solidify her victory on Tuesday night. Her closest opponent, Jacobs, trails 18 points behind her, with 18 percent of the vote, and 16 percent of GOP voters said they are still undecided. Ernst has managed to garner big named endorsements like Sarah Palin, Senator Marco Rubio and Mitt Romney. She's also rallied the support of a wide array of conservative groups, including the U.S. Chamber of Commerce and the Senate Conservatives Fund. Going into the primary, she seems most primed to unify the various factions of the Republican Party against Braley.

IT'S A JUNGLE OUT THERE: California now has a jungle primary, which means the top two candidates-no matter what party-will end up on the general election runoff ballot. It's a boon to independents, about 20 percent of voters in the state, who no longer need to choose a party in order to vote. This is only the second election since the enactment of this new primary system and it's the first featuring candidates for statewide office. California has traditionally been one of the safest states in the nation for incumbents, but the new primary system could change that dramatically, as well as the new voter approved way of drawing House district lines. Now a nonpartisan commission has been given the task of drawing House district lines, taking the job over from the state legislature. The lines beforehand favored incumbents, but this new voter approved measure makes it much more difficult.

THE RACE TO RUN AGAINST JERRY BROWN: It's likely Gov. Jerry Brown will come in first, but who comes in second in the California governor's race? The GOP field includes state assemblyman Tim Donnelly, a tea party favorite and a former leader of the Minuteman volunteer border patrol group. The best funded is Neel Kashkari, a former U.S. Treasury Department official whose has more moderate social views. He has been backed by Jeb Bush. The Republican field also includes a man named Glenn Champ, a registered sex offender who describes himself, according to the LA Times, as "a new breed of Christian soldier." Antiwar activist Cindy Sheehan is also on the ballot as a member of the Peace and Freedom Party. WHY IT MATTERS: Does the new system give a voice to more voters and candidates or squash third party voices? That's something supporters and those who hate the new system are trying to figure out. It won't get solved today, but it's the beginning of a brand new way to vote in America's most populous state and it could catch on elsewhere. Polls show Brown leading easily, but the race for the number two spot remains tight between Kashkari and Donnelly. Establishment Republicans would like to see Kashkari make it to the general election, fearing Donnelly is just too conservative for this blue state.

THE 90210 PRIMARY: California's 33rd congressional district is one of the wealthiest in the entire country and the race to succeed the retiring Henry Waxman, who represented the district for 40 years, is a fierce, as well as a celeb-filled fight. WHY IT MATTERS: The district includes part of the San Fernando Valley and the poshest parts of the state including Beverly Hills, Bel-Air and Malibu. Waxman's retiring has left an opening in a district he won easily most of his elections. Marianne Williamson,a spiritual advisor and best-selling author, has the backing of Katy Perry, Alanis Morissette and Kim Kardashian. The independent candidate is one of 17-yes 17-others, including former prosecutor and Iraq war veteran Elan Carr, NPR talk show host Matt Miller, former state department official Barbara Mulvaney, attorney David Kanuth who has the backing of Gwyneth Paltrow, former City Controller and mayoral candidate Wendy Greuel and state Senator and lieutenant colonel in the U.S. Air Forces Reserves Ted Lieu. Greuel-backed by Emily's List- and Lieu look the likeliest to take the top spots, but with so many candidates and the unpredictability of a primary it's hard to count anyone out.

SANDRA FLUKE RETURNS (OR TRIES TO): Why would a state senate race make this list? Well, that's because Sandra Fluke-made famous thanks to a graphic insult from Rush Limbaugh-is running in the Los Angeles-area state senate district. Fluke, 33, is one of eight candidates running in the most contested of any of the 20 California state senate primary races today. WHY IT MATTERS: Fluke first made a name for herself in February 2012 when as a third-year law student at Georgetown University she testified in front of the House Democratic Steering and Policy Committee in favor of requiring religiously affiliated institutions to cover birth control in health insurance plans. She's trying to win today in her first run for office, benefiting from the higher name recognition she has because of the incident. Her mailers remind voters of the episode that made her famous and she's running on environmental protection issues, affordable education, abortion rights, amongst other issues. Fluke is running against Manhattan Beach Mayor Amy Howorth, Santa Monica-Malibu Board of Education member Ben Allen, former state Assemblywoman Betsy Butler, attorney Barbi S. Applequist, top surgeon for the California National Guard Vito Imbasciani, and former president of the Writers Guild of America Patric Verrone, who has written for television shows including "The Simpsons." Professor at USC Seth Stodder is the lone no party preference candidate. The rest are Democrats. Howorth leads in fundraising.

THE OTHERS:

MAKING THE ROUNDS IN SOUTH DAKOTA: The South Dakota Senate race is considered a strong opportunity for Republicans to pick up a seat and the frontrunner is former Gov. Mike Rounds, endorsed by the Chamber of Commerce and Mike Huckabee. WHY IT MATTERS: Thanks to the retirement of Sen. Tim Johnson, this is the first open Senate seat in South Dakota since Jim Abourezek retired ahead of the 1978 election. Rounds is up against Dr. Anne Bosworth, a doctor of internal medicine, state legislator Stace Nelson, attorney and US Army Reservist Jason Ravnsborg, and state Sen. Larry Rhoden. In November the winner will face the lone Democrat in the race businessman Rick Weiland, as well as two independent candidates: former congressman Larry Pressler and former state Sen. Gordon Howie.

WIDE OPEN SPACES: Three Democrats and three Republicans are seeking their parties' nominations for the Montana Senate race, including Democrat Sen. John Walsh, who was appointed by the governor to serve out the remainder of Sen. Max Baucus' term when he resigned to become the ambassador to China. WHY IT MATTERS: Walsh is up against Lt. Gov. John Bohlinger and rancher Dirk Adams. Walsh has mostly focused his fire on GOP frontrunner Rep. Steve Daines, who is up against state Rep. Champ Edmunds and University of Montana department assistant Susan Cundiff, but Daines looks like he will easily beat his opponent and has also been focused on Walsh. The general election here is likely to be a tight one and a spot Republicans would love to nab.

JERSEY BOYS: Former mayor of Bogota, NJ and tea party favorite Steve Lonegan is facing off against former mayor of Randolph, Tom MacArthur in New Jersey's third congressional district GOP primary. WHY IT MATTERS: MacArthur is the establishment favorite and is considered the frontrunner to replace the retiring Rep. Jon Runyan. Lonegan got an endorsement from Sarah Palin, who backed him last year in his race against Cory Booker in New Jersey's special senate election after the death of Sen. Frank Lautenberg. The winner is likely to go up against Burlington County Freeholder Aimee Belgard.

ABC's Elizabeth McLaughlin and Christopher Good contributed to this report.