Trump and Haley Will Face Off in South Carolina. Here’s What to Know.

The foursome of early Republican nominating contests will soon come to a close with the South Carolina primary, following the Iowa caucuses and New Hampshire primary last month and the Nevada primary and caucuses this month.

Here’s what to know.

When is the South Carolina Republican primary?

Saturday, Feb. 24.

Who can participate?

South Carolina has no formal party registration, so registered voters can participate in the primary regardless of whether they identify as Republicans, Democrats or independents.

However, if you voted in the Democratic primary this month, you can’t vote in the Republican one, too.

How can I vote?

The polls will be open on Election Day from 7 a.m. to 7 p.m. (You can find your polling location here.) You can also vote early from now through Feb. 22 — except for Feb. 18-19 — but your early-voting location may be different from your Election Day polling site, so be sure to check here.

Either way, you’ll need to show photo identification.

Some South Carolinians can cast absentee ballots by mail. You can find out whether you’re eligible for that here.

Unfortunately, if you’re not already registered to vote, it’s too late to do so for this primary; the deadline was last month. But you can find the information you need here to register in time for the nonpresidential primaries in June — when congressional, state legislative and local races will be on the ballot — and the general election in November.

Who will be on the ballot?

Seven candidates will be listed:

• The two major contenders, former President Donald J. Trump and Nikki Haley

• Two little-known candidates, Ryan Binkley and David Stuckenberg

• Three former candidates — Chris Christie, Ron DeSantis and Vivek Ramaswamy — who suspended their campaigns after the ballots were set.

The ballot will also include three questions on policy matters, but those results are not binding; they are intended for the state Republican Party to gauge voter sentiment.

What are we watching for in South Carolina?

South Carolina could be the last stand for Ms. Haley’s campaign.

It is her home state, and voters there twice elected her as governor, so it would seem to provide an opportunity for her to compete closely with Mr. Trump — but polls show her far behind. She has said that she doesn’t think she has to win South Carolina to remain viable but that she needs to do better than she did in New Hampshire (43 percent), which was in turn better than she did in Iowa (19 percent).

If she outperforms the polls, the momentum could carry her into the 16 races of Super Tuesday, where she would need to accumulate a lot of delegates to be competitive. (We’re tracking the delegate count here.) If she doesn’t, her path looks pretty bleak.

What happens next?

After South Carolina, the race will head to Michigan, which will hold its primaries for both parties on Feb. 27 because Democrats moved the state up in their nominating process.

But because the Republican National Committee didn’t authorize that change, it will award only a fraction of Michigan’s delegates to the party’s national convention based on those primary results. The rest of the state’s delegates will be determined later, at caucuses run by party insiders.

After Feb. 27, the weeks of one-state-at-a-time campaigning will end as the race proceeds to Super Tuesday on March 5.