More than a third of all delegates in the Republican and Democratic presidential primaries will be up for grabs Tuesday as voters in 15 states and one territory head to the polls for Super Tuesday.

Democratic President Joe Biden and former President Donald Trump, a Republican, are expected to move to the verge of clinching their parties’ nominations. 

Biden faces only long-shot challengers Rep. Dean Phillips of Minnesota and author and activist Marianne Williamson, who reentered the race last week.

Meanwhile, Trump’s only major competition is former U.S. Ambassador to the United Nations Nikki Haley, who has struggled to close the wide gap between her and her former boss.

The contests

Contests for both parties are being held in Alabama, Arkansas, California, Colorado, Maine, Massachusetts, Minnesota, North Carolina, Oklahoma, Tennessee, Texas, Utah, Vermont and Virginia. 

Alaska is holding its Republican caucuses Tuesday, and American Samoa is holding its Democratic caucuses. 

Also Tuesday, the results of Iowa’s Democratic mail-in caucuses, held in January, will be announced.

Republicans

Trump holds a commanding lead over Haley in the delegate count, 273-43. Another 865 delegates will be awarded Tuesday.

To win the Republican nomination, a candidate must secure 1,215 delegates. 

Haley is coming off her first primary victory Sunday, in the District of Columbia. Trump has soundly beat her in every other primary contest in which they’ve squared off, including a Saturday sweep of Idaho, Michigan and Missouri. 

“If every single conservative, Republican and Trump supporter in these states shows up on Super Tuesday, we will be very close to finished with this primary contest,” Trump said in a video posted Friday on his Truth Social platform. “Republicans will then be able to focus all of our energy, time and resources on defeating crooked Joe Biden, the worst president in the history of our country.”

Haley has remained defiant against pressure from within the party to step aside. 

“We have literally been in 10 states in the past week,” Haley said at a campaign event Monday in Spring, Texas. “We are anywhere and everywhere trying to let people know what their choice is tomorrow. And the choice comes down to this: We can either have more of the same, or we can go in a new direction. More of the same as not just Joe Biden; more of the same as Donald Trump.”

Republican presidential candidate former U.N. Ambassador Nikki Haley speaks at a campaign event in Spring, Texas, Monday, March 4, 2024. (AP Photo/David J. Phillip)

If Haley has any chance of winning the nomination, it would require a seismic shift in voting Tuesday. But she's trailing Trump in virtually all polls -- and by a wide margin in the vast majority of survey. Regardless, her campaign signaled Monday it’s looking beyond it, announcing its leadership team for Louisiana, which does not hold its primary until March 23. 

On Friday, Haley picked up her first two endorsements from current U.S. Senate members when Sens. Lisa Murkowski, R-Alaska, and Susan Collins, R-Maine, announced their support. Their states are among those voting Tuesday. 

Trump secured a major victory on the eve of Super Tuesday, as the U.S. Supreme Court ruled unanimously Monday that Colorado could not block Trump from its ballot after the state’s high court found in December that the former president was disqualified from serving as president over his efforts leading up to the Jan. 6, 2021, storming of the U.S. Capitol.

Colorado and Maine, whose secretary of state had also booted Trump from the ballot under the insurrection clauses, are two of the states voting Tuesday. Because the matter had been unsettled, his name was already set to appear on both states’ ballots.

“I think it will go a long way towards bringing our country together, which our country needs,” Trump said Monday of the Supreme Court ruling. “While most states were thrilled to have me, there were some that didn't. And they didn't want that for political reasons. They didn't want that because of poll numbers, because the poll numbers are very good. We're beating President Biden in almost every poll.”

Since outlasting everyone but Trump in the Republican field, Haley has sharpened her attacks of her former boss.

In California’s case, it could be longer. Mail-in votes there must be postmarked by Tuesday and received by county elections office by March 12. 

On Monday, she hit Trump for the federal government’s spending during his administration, for his comments that he would encourage Russian President Vladimir Putin to attack NATO countries that had not met their financial obligations to the alliance and for his opposition to a bipartisan border and immigration deal.

“Congress needs to get in a room, figure it out and pass a strong border bill, and Donald Trump needs to stay out of it,” Haley said. “We can't wait.”

Trump on Sunday criticized Haley, calling her “Birdbrain” and “a loser.” 

The posts on his Truth Social platform followed Haley’s comments on NBC News’ “Meet the Press,” in which she said she’s no longer obligated to honor her pledge of endorsing Trump if he is the GOP nominee.

“I enjoy watching the Bird disavow her PLEDGE to the RNC and her statement that she would NEVER run against President Trump (‘A great President’),” Trump wrote. “Well, she ran, she lied, and she LOST BIG!”

Democrats

To date, Biden has secured 206 of 208 delegates, with two going to “uncommitted.” Another 1,420 delegates will be awarded Tuesday, and 1,968 are needed to lock up the nomination.

With the exception of the New Hampshire primary — in which Biden’s name had to be written in and the contest was not sanctioned by the party — no challenger has received more than 3% of the vote in a primary. 

The Biden campaign has not paid much mind to Phillips and Williamson and instead has been in general election mode. It has focused its efforts on attacking Trump, most recently on issues including in vitro fertilization, abortion and the bipartisan border deal he helped kill.

President Joe Biden delivers remarks during a visit to the southern border, Thursday, Feb. 29, 2024, in Brownsville, Texas. (AP Photo/Evan Vucci)

While he’s expected to cruise to the Democratic nomination, Biden was hit with a wave of concerning polls in recent days.

Among them, separate polls by New York Times/Sienna College and CBS News had Trump leading Biden by four percentage points in a general election matchup, and an Associated Press-NORC Center for Public Affairs Research poll found that 63% of U.S. adults say they’re not confident in Biden’s mental stability to serve effectively as president. (Fifty-seven percent said that Trump lacks the memory and acuity for the job.)

In an interview with Fox News on Sunday, Sen. Chris Coons, D-Del., Biden’s campaign co-chair, downplayed the polls.

“We have consistently, as Democrats, overperformed polls, not just in the special election that just happened in Long Island, in the midterms in '22, but in election after election,” he said.

Down-ballot races

The presidential race might be the headliner, but there are key races lower on the ballot in some states with national implications.

Among them:

• California is holding the primary for U.S. Senate to fill the seat formerly held by Dianne Feinstein, who died in September. The candidates include Democratic Reps. Barbara Lee, Katie Porter and Adam Schiff, and former Major League Baseball star Steve Garvey, a Republican. In California, the top two vote-getters, regardless of party affiliation, advance to the general election. Schiff and Garvey have been leading in most recent polls. Gov. Gavin Newsom appointed Laphonza Butler, president of the abortion-rights group Emily’s List, to serve until the special election. Butler is not seeking a full term.
  
  
• North Carolina is holding its gubernatorial primary to replace term-limited Democratic Gov. Roy Cooper. Democratic Attorney General Josh Stein and Republican Lt. Gov. Mark Robinson are the favorites to advance to the general election.
  
  
• In Texas, nine Democrats are vying to take on Republican Sen. Ted Cruz, who is seeking a third term, in November. The field includes U.S. Rep. Colin Allred, state Sen. Roland Gutierrez and state Rep. Carl Sherman Sr.

Closing time

The polls begin closing at 7 p.m. Eastern, in Vermont and Virginia.

Because of the number of states and wide geographical range, it could be well into the night for some before results are in. 

In California, mail-in ballots must be postmarked by Tuesday but can still be received up until March 12, meaning some close races might not be settled for days.