And West Virginia Gov. Jim Justice, who made headlines in 2017 when he switched his affiliation from the Democratic Party to join the GOP, is now facing opposition as he asks Republican voters to give him the nomination for a second term.

In total, five states are holding primaries on Tuesday, though much of the voting is taking place via mail ballots. Polls close in Georgia and South Carolina at 7 p.m. Eastern Time, in West Virginia at 7:30 p.m., in North Dakota at 9 p.m. and in Nevada at 10 p.m.

Here are five things POLITICO’s campaigns team is watching in Tuesday’s primaries:

Ossoff’s return?

Ossoff is the frontrunner in the race to face GOP Sen. David Perdue, but Georgia’s runoff threshold looms as a potential, if temporary, obstacle.

Seven candidates make up the primary field, including Ossoff, former Columbus Mayor Teresa Tomlinson and businesswoman Sarah Riggs Amico, the party’s lieutenant governor candidate in 2018. The race goes to an August runoff between the top two candidates if no one tops 50 percent Tuesday.

Polling has shown Ossoff to be the clear frontrunner but below that 50 percent margin, with about one-quarter of primary voters undecided, giving him a potential path to winning the race outright and avoiding extending the primary by eight weeks. If he doesn’t top 50 percent, Tomlinson would be the most likely to challenge him in a runoff, though Amico has been in contention in the recent polling.

Georgia’s status as an emerging battleground state hasn’t made this seat a top priority for the national party so far. The Democratic Senatorial Campaign Committee hasn’t endorsed a candidate despite backing challengers in almost every other primary race, and no outside spending is booked by either party for the fall yet.

Perdue holds a massive cash on hand advantage over whoever emerges as Democrats’ nominee. But Ossoff has fundraising experience from his House race, and Democrats expect the state to be competitive in the fall.

The race has largely been overshadowed by the special election for Georgia’s other Senate seat, which does not have a primary election Tuesday but is an all-party contest in November. There would be a January 2021 runoff if no candidate wins 50 percent of the vote in both races.

Georgia’s congressional showdowns

Two House districts near Atlanta are central to the battle for the majority and show how the changing suburbs have shaped politics in the Trump era.

Georgia’s 7th District hosted the closest House race in the country in 2018, when Democrat Carolyn Bourdeaux, who received little national attention, surprisingly came within 450 votes of ousting GOP Rep. Rob Woodall. Woodall is calling it quits this cycle, and Tuesday’s primary will determine the 2020 matchup for his suburban Atlanta seat.

Both parties could be forced into runoffs. On the Democratic side, Bordeaux is running again and is likely to advance, along with either state Rep. Brenda Lopez Romero or Nabilah Islam, an organizer backed by Rep. Alexandria Ocasio-Cortez (D-N.Y.)

The top GOP contenders are Rich McCormick, a physician and veteran, and state Sen. Renee Unterman, the sponsor of the state’s “heartbeat” abortion bill. McCormick has enjoyed outside help from the Club for Growth and has an endorsement from newly elected Rep. Mike Garcia (R-Calif.), who flipped a House seat last month in a special election.

This race will be a top battleground that draws millions in outside spending, as will the neighboring 6th District, where former Rep. Karen Handel is expected to clear Tuesday’s primary, setting up a rematch with Democratic Rep. Lucy McBath.

Republicans will also winnow fields in two open safe red seats held by retiring Rep. Tom Graves and Rep. Doug Collins, who is running for Senate. One candidate for Collins' seat is a familiar name: Paul Broun, a conservative former congressman about whom some Republicans fretted when he ran unsuccessfully for Senate in 2014 because of his history of inflammatory comments.

Republicans try to avoid a runoff in a top South Carolina pickup

The House GOP will get one step closer to choosing a challenger to take on Rep. Joe Cunningham (D-S.C.), who scored an upset last cycle in a Lowcountry district that Trump carried by a whopping 13 points.

Four Republicans are vying for the nomination, and the primary will advance to a runoff if no one clears 50 percent. Party recruiters are hoping for an outright win by state Rep. Nancy Mace, the first female graduate from The Citadel. She’s supported by the conservative Club for Growth and House Minority Leader Kevin McCarthy.

Mace’s top competition is Kathy Landing, a longtime county councilwoman backed by the political arm of the House Freedom Caucus. But a runoff here wouldn’t be too devastating to the GOP: It would take place just two weeks from the primary and allow them to avoid drawn out battles like the ones they will face in Texas and Georgia.

Either way, Republicans are on track to add at least one more female nominee a week after five women won last Tuesday’s primaries.

Can “Big Jim” navigate a party switch?

The last time Jim Justice was on the ballot in West Virginia, he had a “D” next to his name. Now, the first-term West Virginia governor is trying to win a Republican primary.

It hasn’t been smooth sailing for Justice, who announced his much-ballyhooed 2017 party switch at an appearance with President Donald Trump. Justice’s former commerce secretary, Woody Thrasher, has outspent Justice on the airwaves by a more than two-to-one margin, according to Advertising Analytics, dropping nearly $2.3 million.

Justice has Trump’s endorsement, including another tweet on Sunday urging West Virginia Republicans to vote for “Big Jim Justice,” a reference to the governor’s husky, 6-foot-7 frame.

But party switchers sometimes struggle to win over voters who were accustomed to opposing them. The last major statewide official to change from one party to the other during his term, then-Sen. Arlen Specter of Pennsylvania in 2009, was defeated in a Democratic primary a year later.

A battle of the Dans in Nevada

Rep. Susie Lee (D-Nev.), one of 30 Democrats in a Trump-won district, will get a challenger on Tuesday. The GOP primary for her Las Vegas-based seat has turned into a battle between Dan Rodimer, a former pro wrestler who appeared on World Wrestling Entertainment, and Dan Schwartz, a former state treasurer, who unsuccessfully ran for governor in 2018.

Rodimer is a 2018 state Senate candidate who is running as a staunch Trump ally, and he appears to be the pick of Washington Republicans. He has endorsements from McCarthy and the national super PAC ESAFund, which has run ads knocking Schwartz as insufficiently supportive of Trump. But Rodimer has been accused of assault three times and was arrested on battery charges in 2010 — something Schwartz and his allies have highlighted as the race has turned negative.

Whoever emerges from Tuesday’s primary will need an infusion of cash to take on Lee, who is sitting on $2 million. Rodimer had $220,000 as of late May, while Schwartz had just $53,000.

In a neighboring district, Republicans will also choose a nominee from a massive field to take on Rep. Steven Horsford (D-Nev.). Top contenders include former state Assemblyman Jim Marchant, veteran Sam Peters, and businesswoman Lisa Song Sutton., But this district, which Hillary Clinton won by 5 points, is a reach for Republicans.