It’s presidential primary day in Nevada, which for a couple of decades has been a key early voting state in the race for the White House.

Three days after a massive victory in South Carolina’s Democratic primary, President Biden is expected to score a second straight landslide in Nevada.

But things are far from simple in the Republican primary, where only one of the two major contenders left in the battle for the 2024 GOP presidential nomination will appear on the ballot.

Nikki Haley, the former two-term South Carolina governor who later served as U.N. ambassador in former President Donald Trump’s administration, is the sole remaining candidate listed in the state-run Republican primary contest.

But Trump, who is the commanding front-runner for the GOP nomination as he makes his third straight White House run, isn’t on the ballot. Instead, Trump will be listed two days later, in a presidential caucus being run by the Nevada GOP.

The genesis of the competing contests dates back to 2021, when Democrats, who at the time controlled both Nevada’s governor’s office and the legislature, passed a law changing the presidential nominating contest from long-held caucuses to a state-run primary.

The Nevada GOP objected, but last year their legal bid to stop the primary from going forward was rejected. In a twist, the judge in the case allowed the state Republicans to hold their own caucuses. No delegates will be at stake in the Republican primary, while all 26 will be up for grabs in the GOP caucus.

The state GOP ruled that candidates who put their name on the state-run primary ballot could not take part in the caucuses.

Haley and some of the other now-departed Republican presidential candidates viewed the Nevada GOP as too loyal to Trump and decided to skip a caucus they believed was tipped in favor of the former president.

Nevada GOP chair Michael McDonald and both of the state’s members of the Republican National Committee are supporting Trump.

“We made the decision early on that we were not going to pay $55,000 to a Trump entity that, you know, to participate in a process that was rigged for Trump,” Haley campaign manager Betsy Ankney argued on Monday.

While Trump’s assured of winning all 26 delegates at stake, sources say he and his campaign advisers have some concerns. An unpleasant potential scenario for Trump, who won both the Iowa caucuses and the New Hampshire primary by double-digits, could be Haley grabbing more votes in the primary than Trump lands in the caucus.

While the GOP presidential candidates had to choose either the caucus or primary ballot, registered Republicans in Nevada can vote in both contests.

And in the GOP primary, there’s no vehicle for voters to write in Trump’s name. The choices on the ballot are Haley and a “none of these candidates” option.

Trump’s campaign has been working to get the message out to supporters in Nevada that if they want to vote for the former president, they need to show up at the caucuses.

“Your primary vote doesn’t mean anything. It’s your caucus vote,” Trump said at a rally in Las Vegas late last month. “So in your state, you have both the primary and you have a caucus. Don’t worry about the primary, just do the caucus thing.”

Republican Gov. Joe Lombardo, who is supporting Trump, told the Nevada Independent last month that he would vote for “none of the above” in Tuesday’s primary, and would caucus for Trump in the state GOP’s contest on Thursday.

A source in the former president’s political orbit told that team Trump is “fortunate that Haley doesn’t have her act together in Nevada.”

Trump is expected back in Las Vegas on Thursday, for a caucus celebration.

Haley is not returning to Nevada this week and hasn’t campaigned in the state since speaking in late October at the Republican Jewish Coalition’s annual leadership conference.

“In terms of Nevada, we have not spent a dime nor an ounce of energy on Nevada,”Ankney told reporters. “So Nevada is not and has never been our focus.”

This week’s contests are just an appetizer for Nevada, which as a key general election battleground state will see plenty of campaign traffic this summer and autumn.