Tuesday marks the first big primary day of 2018. Voters go to the polls in Indiana, Ohio, West Virginia and North Carolina.

Most of the exciting action is on the Republican side. In all of those states (except for North Carolina), Democratic senators are trying to hold on to seats in territory President Donald Trump won in 2016, which means the GOP primaries are high-stakes contests. (More on that below.)

But there’s also plenty to watch at the House level, including the near certainty that the vice president’s brother is coming to Congress.

1. Senate slugfests  

The drama in Indiana and West Virginia, long dubbed the nastiest GOP primaries in the country, just won’t stop. Everyone wants to be Trump’s best friend, which has led to name-calling, ad photoshopping and lots of cardboard cutouts.

Both three-way contests are unpredictable. The biggest question: Will two self-funders who bill themselves as political outsiders come away with the nominations?

In Indiana, businessman and former state Rep. Mike Braun is thought to have an edge. He’s spent nearly $6 million of his own money on the race, and likely much more by the time Tuesday comes and goes. But his opponents stepped up the attacks against him this weekend for having voted in Democratic primaries in the past.

And in West Virginia, former Massey Energy CEO Don Blankenship, another self-funder, has seen a late resurgence. National Republicans had already spent upward of $1 million against him, and on Monday Trump followed up with a tweet about how the former convict would be unelectable in November.

For much of the past year, GOP Rep. Evan Jenkins and state Attorney General Patrick Morrisey went after each other. But Morrisey turned his fire on Blankenship this weekend, releasing a last-minute digital ad on Monday highlighting his conviction for conspiring to violate mine safety standards in connection with the Upper Big Branch mine explosion that killed 29 miners in 2010. 

Another common dynamic in both primaries: Jenkins in West Virginia and Braun in Indiana are being attacked for having voted Democratic in the past. It’s an obvious hit in states where Hillary Clinton lost by large margins. But there are arguments to be made that those attacks don’t resonate in areas of the country that were traditionally home to conservative Democrats. Still, it’ll be interesting to see how those attacks ultimately land, since at least two other GOP Senate candidates who were previously Democrats are running in other states this year.

The Senate primary in Ohio is far sleepier, with Trump outright endorsing Rep. James B. Renacci, who also secured the backing of the entire GOP delegation. 

Watch: 5 Things to Watch in Tuesday’s Congressional Primaries

2. Brotherly love (or not)

Voters in Indiana’s 6th District are likely to nominate Greg Pence, the older brother of Vice President Mike Pence. And since it’s a safe Republican seat, he’s likely coming to Congress, where he’ll have to confront many of the reporters he’s shied away from on the campaign trail (and at his antique mall).  

The Pences may not be the only Hoosier brothers in Washington together next year. Former state Rep. Steve Braun, the brother of Senate candidate Mike Braun, is running for the GOP nod in the open 4th District. They share a slight physical resemblance, but haven’t wanted much to do with each other on the campaign trail. 

Steve has put his own money into the race, albeit nowhere near as much as Mike has poured into the Senate contest. Meanwhile, a mysterious super PAC with a North Carolina P.O. Box has been spending on mailers against two of Braun’s opponents in the 4th District.

3. Will an incumbent lose? 

It’s a so-called blue moon year in North Carolina, which means there are no statewide races at the top of the ticket. All the action is at the House level. In the 9th District, GOP Rep. Robert Pittenger could become the first incumbent of the cycle to lose. He’s facing off against former pastor Mark Harris, whom he defeated by just 134 votes in a recount in 2016. Pittenger’s thought to be in better shape this year. The general election, though, could be a different story, since his likely Democratic opponent has outraised him. Another incumbent to keep an eye on: 3rd District GOP Rep. Walter B. Jones, who’s no stranger to primaries. 

4. A familiar proxy fight

The next big special election is in Ohio’s 12 District in August. GOP Rep. Pat Tiberi vacated the seat earlier this year, and Inside Elections with Nathan L. Gonzales rates the race Tilts Republican. Voters will vote twice on Tuesday’s ballot — once on the candidates who will face off in August’s special election to fill the remainder of Tiberi’s term and once on the nominees who will face off in November.

The crowded Republican primary has turned into a familiar tug of war between the conservative and establishment factions of the GOP. The political arm of the House Freedom Caucus and Ohio Rep. Jim Jordan, the group’s founder, are backing businesswoman Melanie Leneghan, while Tiberi and the Republican Main Street Partnership are backing state Sen. Troy Balderson. Each side argues its candidate stands a better chance of fending off Democrats in a special election that’s increasingly on the radar.

5. A win for GOP women?

For years, Republican strategists have recognized they need to help women through primaries, especially in safe GOP seats, to help diversify their ranks in the House. And in one West Virginia primary, there’s a small sign the party is putting its money where its mouth is. Winning for Women Inc. recently made a five-figure digital investment for state House Del. Carol Miller, who’s running in a crowded GOP field for the nomination in the open 3rd District. If she wins, that independent expenditure won’t be what makes the difference, but it could inspire outside groups to play for more women in primaries down the road.