Here's what you need to know about today's primary elections

Four states have primary elections on Tuesday: Indiana, North Carolina, Ohio, and West Virginia. Senate seats, House seats, and even a governorship are in play. Here's what you need to know.

Indiana

SENATE: Two Republican Congressmen, Rep. Todd Rokita and Rep. Luke Messer, are running against former state lawmaker Mike Braun. Whoever wins this very heated primary will take on incumbent Democratic Sen. Joe Donnelly.

All three Republicans are playing up their support for President Donald Trump before this election. Rokita, who is outspokenly tough on immigration and promised to vote for a border wall, ran an ad bashing special counsel Robert Mueller's investigation as a "witch hunt." Braun, who broke convention by not wearing a suit jacket to the debate, is painting himself as an outsider like Trump. “President Trump, he was a disrupter, outsider and businessman, and look what’s occurred,” Braun told Fox News. Meanwhile, Messer wrote a letter nominating Trump for a Nobel Peace Prize, and got 17 other members of Congress to sign it.

CONGRESS: Indiana's 2nd and 9th Congressional districts are both currently held by Republicans, but both are seen as districts that Democrats could feasibly win this year. The Democratic Congressional Campaign Committee has listed the 9th district as one of its targets, and Tuesday's election will determine if the DCCC's hopes will be riding on civil rights lawyer Dan Canon, labor attorney Liz Watson, or truck driver Ron Chatlos who has reportedly raised no money this entire campaign.

North Carolina

CONGRESS: North Carolina's 2nd, 9th, and 13th Congressional districts are all held by Republicans, but incumbent Rep. Robert Pittenger is facing a tight race against Mark Harris, who only lost to Pittenger by 134 votes in the 2016 primary.

All three Republican candidates may face close races in November from Democrats. In the 13th district, Democrat Kathy Manning outraised Republican incumbent Ted Budd three-to-one in the first three months of this year.

Ohio

U.S. SENATE: Two Republicans, Rep. Jim Renacci and businessman Mike Gibbons, are vying for the GOP nomination. Once they have that, they'll try to take on the state's Democratic Sen. Sherrod Brown. President Trump has endorsed Renacci.

U.S. HOUSE OF REPRESENTATIVES: Democrats are hoping to win the 1st, 7th, 10th, 12th, 14th, and 15th Congressional districts in Ohio, taking six more seats in Congress.

GOVERNOR: Since Ohio's governor is limited to two consecutive terms, Gov. John Kasich (R) cannot run for re-election. Kasich was first elected governor in 2010, and then again in 2014.

On the GOP side: State Attorney General Mike DeWine is facing off against Lt. Gov. Mary Taylor. The two campaigns have taken to fighting each other on Twitter, with Taylor suggesting that DeWine was not attending Trump's events in Ohio because they "just happen to fall during nap time" for the 71-year-old. Meanwhile, DeWine took a page out of Trump's anti-Hillary playbook and tweeted the hashtag #LockHerUp about Taylor. DeWine's tweet has since been deleted.

On the Democrat side: Rich Cordray, the former head of former President Barack Obama's Consumer Financial Protection Bureau, is running against Dennis Kucinich, who represented Ohio in Congress until 2013 and ran (unsuccessfully) for the Democratic nomination during the 2004 and 2008 presidential primaries.

West Virginia

SENATE: On the GOP side, Rep. Evan Jenkins, Attorney General Patrick Morrisey, and former coal baron Don Blankenship are all fighting for a chance to run against incumbent Joe Manchin (D). Manchin is one of the most centrist Democrats in the Senate, and is expected to easily win his primary against Paula Jean Swearengin.

In a tweet on Monday, Trump endorsed Jenkins and Morrisey, and told voters to "remember Alabama" because "Don Blankenship, currently running for Senate, can’t win the General Election in your State...No way!" Trump was referring to the 2017 special election to fill Attorney General Jeff Sessions's seat in Alabama, where Republican Roy Moore (who beat the Trump-endorsed candidate, Luther Strange, in the primary) lost to Democrat Doug Jones in the general election. Blankenship has become a lightning rod for controversy after running an advertisement that claimed that Senate Majority Leader Mitch McConnell (R-Ky.) was creating jobs for "china people." The ad also claimed that McConnell's "China family" — an apparent reference to McConnell's wife, Secretary of Transportation Elaine Chao — "has given him tens of millions of dollars."

When confronted about this ad, Blankenship responded, "We’re confused on our staff as to how it can be racist when there’s no mention of race... There’s no race. Races are Negro, white Caucasian, Hispanic, Asian."

Blankenship was also recently released from prison for his role in a coal mine explosion that killed 29 miners.

To the great people of West Virginia we have, together, a really great chance to keep making a big difference. Problem is, Don Blankenship, currently running for Senate, can’t win the General Election in your State...No way! Remember Alabama. Vote Rep. Jenkins or A.G. Morrisey!

— Donald J. Trump (@realDonaldTrump) May 7, 2018

CONGRESS: With Rep. Evan Jenkins running for U.S. Senate, his seat in the House of Representatives is back in play. Conrad Lucas, the former state chair of Republican Party is running against state delegate Carol Miller for the GOP nomination.