It’s The Biggest Primary Day Of the 2018 Midterms. Here’s What To Watch For

Welcome to 2018's Super Tuesday.

Voters head to the polls in eight states to pick nominees for Senate seats, governor, and several key congressional races that could decide control of the House of Representatives this fall.

Mississippi, Alabama, Iowa, Montana, New Jersey, New Mexico and South Dakota all vote Tuesday. But — with good reason — most of the national focus is on California.

Democrats see their path to the House majority running through the two dozen districts that sent a Republican to Congress in 2016 but voted for Hillary Clinton over Donald Trump. Seven of these districts are in California, with the highest concentration in the longtime Republican outpost of Orange County.

Sensing a Democratic surge, Republican incumbents Ed Royce and Darrell Issa retired, raising Democratic hopes even higher in those races.

"Top two" drama

But Democrats may have gotten too excited about these pickup opportunities for their own good.

Many of these Southern California districts are crowded with Democratic candidates. In California's unusual top-two primary system, all these Democrats and Republicans are competing on the same ballot. The top two vote getters advance to November, regardless of party affiliation. Democratic leaders are worried the large Democratic fields will spread out their party's votes, allowing two Republicans to advance in some of these races and taking away what should be competitive fall campaigns.

The Democratic Congressional Campaign Committee and other national groups have spent millions of dollars trying to stave off a November shutout in the 49th, 48th and 39th congressional districts.

While Democrats are sweating out this nightmare scenario on the local level, California Republicans have their own top-two fears in statewide races. A crowded field is running to replace term-limited Gov. Jerry Brown in the statehouse, and Sen. Diane Feinstein is running for another term. In both of these marquee races, there is a realistic possibility that Democrats' substantial statewide voter registration edge over the GOP will lead to Democrat vs. Democrat ballots.

While Republicans would be likely to have a hard time winning either the governorship or a Senate seat this fall, party leaders are worried all-Democratic ballots would depress GOP turnout, hurting more competitive down-ballot races.

Governors' mansions up for grabs

A crowded — very crowded — field is vying to replace Democrat Jerry Brown, who is wrapping up his second eight-year stint as California's governor. Lt. Gov. and former San Francisco Mayor Gavin Newsom has led post polls. Republican businessman John Cox and Democrat Antonio Villaraigosa appear to be fighting for the second spot on the fall ballot, along with many other candidates.

In Iowa, several Democrats are competing to take on Republican Gov. Kim Reynolds this fall. Iowa Democrats have seen their power and relevance wane in recent years and are hoping to claw their way back into power in 2018. The Democratic primary saw a major last-minute plot twist, when state Sen. Nate Boulton suspended his campaign after several women accused him of sexual misconduct.

Several Republicans are challenging Alabama Gov. Kay Ivey, who succeeded Gov. Robert Bentley after he resigned. The GOP primary took a nasty and personal turn when another candidate raised unfounded rumors about Ivey's personal life, which she aggressively denied. The Democratic primary has seen more energy than usual in the solidly Republican state, coming so soon after Democrat Doug Jones' shocking victory in last year's special Senate election.

Senate seats

Two Democratic Senate primaries are worth keeping an eye on Tuesday, though in both cases, the incumbents are expected to prevail.

California Sen. Dianne Feinstein is one of the few moderate Democrats up for re-election this year to face a serious primary challenge from the left. Former state Senate President Pro Tem Kevin de Leon argues Feinstein isn't doing enough to oppose the Trump administration. Feinstein has responded to the challenge by tacking to the left and leads de Leon in most polls.

New Jersey Democrat Robert Menendez is facing a primary challenge, as well. Menendez is favored to win against Lisa McCormick, but this is the first time he is facing voters after a lengthy corruption trial ended with a hung jury.

In Montana, Republicans are picking their nominee to face Democrat Jon Tester in November. President Trump has made Tester a top target, after the Democrat played a key role in tanking Trump nominee for secretary of veterans affairs Ronny Jackson. State Auditor Matt Rosendale and former Judge Russ Fagg are the top contenders for the GOP nomination.

Will more GOP House members struggle?

In Alabama, Rep. Martha Roby is trying not to become the second House incumbent to lose a primary this year. The Republican came under fire from conservatives after she said she wouldn't vote for Trump following the release of the Access Hollywood video in October 2016, in which Trump made vulgar comments about women. Now, Roby faces a primary challenge from Rich Hobson — who managed Roy Moore's controversial and failed Senate campaign last fall — and her predecessor, former Democratic Rep. Bobby Bright, who is now running as a Republican and Trump loyalist. If no candidate tops 50 percent on Tuesday, the top two candidates will face a July runoff.

Meanwhile, South Dakota Rep. Kristi Noem could be the latest member of Congress to struggle this cycle in a bid for statewide office. She is seeking the GOP nomination for governor against Attorney General Marty Jackley, who has tried to tar her as part of the D.C. establishment. Other Republican House incumbents have underperformed in their races so far this year, and Idaho Rep. Raul Labrador lost his primary bid for governor. How Noem performs could show whether even being part of Congress is a kiss of death with GOP primary voters.

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