Voters in Colorado, Maryland, Mississippi, New York, Oklahoma, South Carolina and Utah head to the polls Tuesday in a slate of primaries that highlight the many fissures in both political parties that continue to define a contentious 2018 primary season.

South Carolina and Mississippi are holding runoff elections, and New York state is holding its primary election for federal offices on Tuesday, meaning the high-profile battle between Gov. Andrew Cuomo and Sex and the City actress Cynthia Nixon will have to wait until September.

Key gubernatorial races Tuesday include Colorado, where an openly gay Democratic multi-millionaire and a cousin of the Bush family are hoping to out-duel a crowded field of challengers, and Maryland, where two well-connected African-American Democrats are vying for the chance to defeat one of the nation's most popular governors in GOP incumbent Larry Hogan.

Over 50 U.S. House seats are at stake in November in the states voting Tuesday, and Democrats are eyeing a number of swing seats in both central and upstate New York, as well as Salt Lake City-based seat held by GOP Rep. Mia Love, one of the few sitting African-American Republicans in Congress.

The marquee race in South Carolina is the Republican runoff election between sitting Gov. Henry McMaster and businessman John Warren. While McMaster has the backing of President Trump, Warren is making the case that he can best implement the president's agenda in the state.

Here's a look at some of the key storylines and races to watch on Tuesday.

Republicans try to reverse Colorado's blue trend in governors race

The Republican slot in November's Colorado gubernatorial election appears to be state Treasurer Walker Stapleton's (a cousin of the Bush family) to lose as conservatives eye the Centennial State as a chance to break a potential "blue wave," and wrestle back control of the governor's mansion after eight years Democrat John Hickenlooper's administration.

Stapleton and his primary opponents Victor Mitchell, Doug Robinson and Greg Lopez have approached their orientation to President Donald Trump with a cautious embrace.

At last week's debate, each expressed their overall support for the president but denounced a recent policy of separating migrant families at the border. Only Robinson offered a full refute of the White House's immigration policy.

U.S. Rep. Jared Polis, D-Colo., and former Colorado Treasurer Cary Kennedy have emerged as clear front-runners in the Democratic primary, with former state Sen. Mike Johnston attracting enough out-of-state money (including considerable financial support from Former New York City Mayor Michael Bloomberg) to maintain his dark horse status.

With few substantial policy differences between them, Polis and Kennedy have spent time picking apart each other's campaign tactics, despite signing a clean campaign promise.

Colorado Republicans hope enough self-inflicted wounds within the Democratic primary opens up a path to the state's first Republican governor in a decade.

Utah part of Dem push to steal red seats

Incumbent Republican Rep. Mia Love is unopposed in her primary bid that is only a formality as she prepares to face Democratic candidate Ben McAdams, the Salt Lake County mayor, this fall.

McAdams has also already cleared the field through the Democratic state party’s convention – setting up a battleground race in one of the country’s most purple districts.

So far, Love, a Haitian-American, has not suffered any public rebuke from President Trump, whom she has at times disassociated herself from, particularly when she condemned the president’s comment that Haiti was a "shithole country."

But Love has also put politics aside to work with the president to help her district when she personally appealed to the president to secure the release of Joshua Holt, who was held in Venezuela.

"She didn’t forget," Trump said, crediting Love for advocating for Holt’s release. "She was out there pitching."

Love also teamed with other moderates to launch the immigration discharge petition and has criticized the administration’s practice of separating immigrant children from their parents while they face prosecution.

McAdams made local headlines earlier this month when he vetoed a controversial development project that would have generated 33,000 new city residents in 9,000 housing units. Love had criticized McAdams for accepting campaign contributions from principals behind the development.

Recent polling shows a tight race within the margin of error, with Love attracting 47 percent of likely voters and McAdams garnering 43 percent in a poll conducted by Dan Jones & Associates from May 15 to June 5.

Utah is also voting to legalize medical marijuana and former Republican presidential nominee Mitt Romney is on the ballot running for U.S. Senate. Both factors could impact voter turnout.

Democrats in Maryland try and crack the code to beating Hogan

Republican Larry Hogan is running for a second term and has earned the reputation as one of the most popular governors in the country despite running arguably one of the nation's bluest states.

The crowded field vying to unseat Hogan has consolidated around two well-connected members of the Democratic Party in Maryland: former NAACP President Ben Jealous and Prince George's County Executive Rushern Baker. However Baker and Jealous represent a geographic split in the state party; Baker's base of support lies in the suburbs outside of Washington, D.C. where he holds elected office, while Jealous has stronger support in Baltimore, where the NAACP is based, and the surrounding area.

Jealous says his campaign is "a movement on Donald Trump's doorstep," has touted and utilized support from a number of prominent national figures in the Democratic Party, including Sen. Kamala Harris of California, Sen. Bernie Sanders of Vermont (who still maintains his status as an Independent who caucus with Senate Democrats), and has brought in national celebrities like Dave Chappelle to campaign for him in recent weeks.

Baker has the support of Sen. Chris Van Hollen and former Governor and presidential candidate Martin O'Malley.

The race will provide a key data point in the debate within the Democratic party over whether or not a campaign that draws more on national themes like Jealous' is a more effective strategy in defeating Republicans who are not as closely tied to the Trump-brand like Hogan.

A bare-knuckle, Trump-centric brawl on Staten Island

Staten Island is playing host to the most raucous GOP primary that will be settled Tuesday, where GOP Rep. Dan Donovan and former congressman and convicted felon Michael Grimm have repeatedly clashed over who President Trump prefers in the race.

Staten Island is playing host to the most raucous GOP primary that will be settled Tuesday, where GOP Rep. Dan Donovan and former congressman and convicted felon Michael Grimm have repeatedly clashed over who President Trump prefers in the race. Grimm went as far as accusing Donovan of offering to get him a presidential pardon for political reasons.

Donovan acknowledges that he discussed a potential pardon for Grimm with President Trump aboard Air Force One last month, but says the President dismissed the idea after Donovan told him one of Grimm's political mentors was a "Never Trumper" who did not support him in the 2016 election.

Whoever emerges from a bruising GOP primary will likely go on to face Democrat and U.S. Army veteran Max Rose, who is part of the Democratic Congressional Campaign Committee's (DCCC) "Red to Blue" program for top-tier candidates.

A South Carolina runoff over who has run afoul of Trump

The first round of voting in the GOP gubernatorial primary in South Carolina revolved around President Trump, and the second round is no different.

Incumbent Gov. Henry McMaster is accusing his opponent, businessman John Warren, of being a "Never Trumper" and lying on the campaign trail, while Warren fired directly back at McMaster saying his "endless connections to corruption are why 58% of people voted against" him in the first round of primary voting.

President Trump is campaigning for McMaster in the state on Monday, and Vice President Pence paid a visit over the weekend to boost the incumbent.

McMaster, the former lieutenant governor, stepped in to replace former Governor Nikki Haley, who assumed the post of U.S. Ambassador to the U.N. under President Trump. McMaster was the first statewide official in South Carolina to endorse Trump in 2016 and Trump returned the favor by offering McMaster his first gubernatorial endorsement of the 2018 cycle.

McMaster won the first round over Warren by nearly 15 points and the winner of Tuesday’s runoff will face Democratic nominee State Rep. James Smith, who has the backing of former Vice President Joe Biden and longtime South Carolina Congressman James Clyburn.

Other key races to watch

Colorado 6th Congressional District: Incumbent Republican Mike Coffman won re-election in 2016 with just 51 percent of the vote in a district that Hillary Clinton won by nine points. Coffman had declined to endorse Trump and actively campaigned on a promise to stand up to a potential Trump presidency in an effort to appeal to moderate voters in his suburban Denver district. Despite Coffman’s willingness to criticize the President, it may not be enough to save him this year.

Coffman was able to stifle a potential primary challenge at his nominating convention, but Democrats see Coffman’s seat as an important potential pickup as they plan a potential path to a majority. Two Democrats, attorney and Army veteran Jason Crow and businessman Levi Tillemann, are running, but Crow has a large fundraising advantage, with over $1.2 million compared to Tillemann’s total of just over $277,000.

Maryland U.S. Senate: Incumbent Ben Cardin is running for reelection and has a wide lead in the polls, but is facing a challenge from controversial whistleblower Chelsea Manning. A court-martial sentenced Manning to a prison term for violating the Espionage Act by handing over classified documents to Wikileaks. After having her sentence commuted by President Obama last year, Manning announced a run for Senate this past January. Manning came under fire for having several contacts with alt-right figures, something Manning claimed was part of an effort to infiltrate their circles.

Cardin, meanwhile, has still raised ample funds despite being relatively safe in both his primary and general election challenges. Cardin has raised over $2.7 million this cycle, while Manning has raised just under $72,000.

New York 12th Congressional District: Carolyn Maloney has served in Congress for over a quarter-century but faces a well-funded challenge in the Democratic primary from 34-year-old progressive challenger Suraj Patel. Maloney has the backing of New York City’s Democratic establishment, including Mayor Bill De Blasio, but Patel has criticized Maloney as out-of-touch with the district’s sizable millennial population.

In a debate between the two candidates, Maloney went on the offensive and raised concerns about Patel’s business record and voter registration. Reports have emerged of labor violations committed by the hotel company Patel’s family runs and of Patel registering to vote at two different out-of-district addresses. Patel countered by criticizing Maloney for her votes on criminal justice issues, including her support of the 1994 crime bill pushed by President Bill Clinton.

Patel has raised over $1 million in his campaign, keeping him within a few hundred thousand dollars of Maloney’s fundraising totals. But Maloney has triumphed over well-funded primary opponents before. In 2010, lawyer Reshma Saujani raised $1.3 million in her bid but Maloney still won the primary with 81 percent of the vote.

New York 14th Congressional District: In another instance of a New York City race with a longtime Democratic incumbent facing a young progressive challenger, House Democratic Caucus Chair and Queens Democratic boss Joe Crowley faces 28-year-old Alexandria Ocasio-Cortez.

Crowley, the fourth-ranking Democrat in the House, wields sizable influence over Democratic politics both in New York City and on Capitol Hill and has been tipped as a potential candidate for Speaker of the House should Democrats retake the House of Representatives.

Ocasio-Cortez meanwhile has the backing of several progressive organizations, Brand New Congress, Justice Democrats and NYC Democratic Socialists of America. She has focused her campaign engagement on millennials and people of color, a strategy that could help in a district that is nearly half-Hispanic and majority-non-white.

Crowley has the backing of Planned Parenthood Action Fund, NARAL Pro-Choice America, and Giffords, the gun safety organization founded by former Congresswoman Gabrielle Giffords and Captain Mark Kelly.

The primary winner will be heavily favored for re-election against Republican Anthony Pappas.

New York 19th Congressional District: President Barack Obama won the district both times he ran and although President Trump won by six points in 2016, Democrats believe that they can potentially unseat Republican Rep. John Faso.

Top candidates in the seven-person Democratic field include entrepreneur Brian Flynn, businessman Pat Ryan, and attorney Antonio Delgado, all of whom have raised over $1 million so far. Delgado has raised more funds than any candidate in the field, including Faso. In addition, Gareth Rhodes, a former aide to Gov. Andrew Cuomo, has announced his candidacy and is being supported by other former Cuomo staff. Candidate Erin Collier, the sole woman in the race, has the backing of EMILY’s List.

National Democrats have not backed a single candidate in the race but consider Faso a vulnerable incumbent as a congressional freshman in a swing district. In an added wrinkle that could affect the November result, actress Diane Neal, formerly of Law and Order: Special Victims Unit, has announced an independent bid.

New York 21st Congressional District: An eccentric, outspoken and opinionated former television personality decides to run for office as a first-time candidate on a decidedly populist platform. Sound familiar? Former cable news host Dylan Ratigan is one of five candidates running in the Democratic primary against Republican Elise Stefanik and will test whether or not Democrats are ready for a left-wing campaign emulating Donald Trump’s style.

Ratigan, who left his TV show at MSNBC to start a hydroponic farming business and contribute to the left-wing blog The Young Turks, has elicited controversy for saying that he would have voted for Donald Trump had he cast a ballot in 2016. Ratigan, a vocal Bernie Sanders supporter, backtracked and said he had made the remarks in jest.

Former county official Tedra Cobb leads all Democrats in fundraising and has the endorsement of the local chapter of Bernie Sanders’ legacy political organization Our Revolution, while former Democratic delegate Patrick Nelson has the endorsement of Our Revolution’s state chapter.

Stefanik, a two-term incumbent who endorsed Trump in 2016 but has recently criticized the President on issues including tariffs and presidential pardons, is running unopposed in the Republican primary.

New York 24th Congressional District: John Katko has defied the odds in two consecutive elections, winning two terms Congress as a Republican in a district that has voted for the Democratic nominee in the last three presidential elections. But Democrats are making an aggressive push to flip the district, with national Democrats pushing Navy veteran former State Assistant Attorney General Juanita Perez Williams as their candidate of choice.

Perez Williams has prior name recognition as she had previously run an unsuccessful campaign for mayor of Syracuse last year. After her defeat, she jumped into the Democratic primary against Dana Balter, who has the advantage of having the backing of the Working Families Party, a smaller left-leaning party that occasionally co-runs Democratic candidates through a loophole in New York’s electoral system.

Katko has earned a reputation as a relatively moderate Republican in Congress, voting against the Republicans’ 2017 effort to repeal the Affordable Care Act. He will be running unopposed in Tuesday’s primary.

Oklahoma Governor: Republican Mary Fallin leaves office as one of the nation’s most unpopular governors, but the GOP will still have the upper hand in the Sooner State, where Republicans have held a legislative trifecta since 2010 and every congressional seat since 2012.

Ten candidates have declared for the Republican primary and four candidates have polled relatively strongly due to having either lots of money or name recognition: Oklahoma City mayor and former TV anchor Mick Cornett, Lieutenant Governor and former Secret Service agent Todd Lamb, businessman Kevin Stitt, and Gary Richardson, a former independent candidate for Governor.

Former Attorney General Drew Edmondson will face former State Senator Constance Johnson for the Democratic nomination.

South Carolina 4th Congressional District: The departure of House Oversight Committee chairman Trey Gowdy has helped force two runoff elections as both Democrats and Republicans have had to narrow down crowded primary fields in this upstate South Carolina seat. On the Republican side, former State Senator Lee Bright took first place and will face State Senator William Timmons, who survived a recount after narrowly earning the second spot in the runoff.

As a State Senator, Bright made headlines in 2015 when he was one of three Senators to vote against removing the Confederate flag from the South Carolina State House grounds after the Charleston Church shooting.

Democrats will be choosing between accountant Doris “Lee” Turner and education consultant Brandon Brow, who both advanced out of a close first round where three candidates earned between 25 and 30 percent of the vote.

Utah Senate: Last but certainly not least on the docket of races Tuesday night, the political return of one Willard "Mitt" Romney.

In 2016, former Republican presidential nominee Mitt Romney may have called Donald Trump a “con man” and “a fake” and said he would never accept a Trump endorsement again, but Romney changed his tune this past February as he happily accepted President Trump’s endorsement.

The praise from Trump is far cry from the harsh critique Trump offered of Romney in February 2016, calling him "one of the dumbest and worst candidates in the history of the Republican politics."

Romney has stumbled a few times during his candidacy for U.S. Senate, including a loss to conservative challenger and State Representative Mike Kennedy at the GOP convention that forced Romney into this primary. Romney has continued to tamp down his criticism of President Trump on the campaign trail in an effort to appeal to conservative voters, although polling indicates that Romney is still the heavy favorite among the Utah Republican electorate.

Correction: A previous version of this article incorrectly stated that Alexandria Ocasio-Cortez, a Democratic candidate in New York's 14th Congressional District, had the endorsement of NARAL Pro-Choice and Moms Demand Action. Rep. Joe Crowley, the Democratic incumbent in that district, has the endorsement of both of those organizations.