WASHINGTON — The Republican Party’s gambit to kill primary elections to ensure President Trump’s renomination may protect the president from short-term losses but has also put the spotlight on his challengers.

Republicans in four states have canceled presidential primaries next year in an effort, they say, to save money.

Given Trump’s popularity within the party, it’s unlikely the primaries would make a big difference anyway. But canceling primaries could result in more uncommitted delegates to the Republican National Convention next year, meaning they would not be pledged to Trump and could be less loyal if things go sideways.

“The attempts to stifle competition have backfired,” challenger William Weld. “The Republican Party in Washington is working on voter suppression. I’m working on enlarging the electorate.”

Weld has spent the last six days campaigning in New Hampshire and had four cable television news appearances scheduled this week. “The dial-o-meter has dialed way up,” he said.

The former Massachusetts governor, who ran as a libertarian in 2016, has been courting others to join him as anti-Trump Republicans. Joe Walsh and Mark Sanford, two tea party conservatives who lost reelection to Congress, are also running.

“It seems more like a real primary than when I was the solitary standard bearer out there planting my flag,” Weld said.

Polls show Trump remains popular with the overwhelming majority of Republican voters. But his allies’ fear of a runaway primary is founded in history: No modern president has ever won reelection after a serious primary challenge.

Harry Truman and Lyndon Johnson dropped out after poor showings in New Hampshire. Gerald Ford, Jimmy Carter and George H.W. Bush all won renomination but were wounded by challenges from Ronald Reagan, Ted Kennedy and Pat Buchanan.

And even though Weld, Sanford and Walsh don’t pose the same level of threat to Trump, the state Republican parties in South Carolina, Nevada, Arizona and Kansas are preventing history from repeating itself by canceling their nominating contests.

“The logic behind the move was, ‘Circle the wagons and protect the incumbent.’ I get it,” Sanford told Bloomberg Radio on Wednesday. But he said that move doesn’t make sense if Trump is — as he claims — the most popular president ever among Republicans.

“If that is true, you would take the win. You would take 90% all day long, particularly in the first-in-the-South primary,” Sanford said, referring to the primary in his home state of South Carolina. “It suggests that someone looking at the numbers is concerned, and that his support is a mile wide and an inch deep.”

Trump’s challengers don’t have to win the nomination to hurt his chances of reelection. Buchanan lost New Hampshire with 37% of the vote in 1992, but exceeded expectations and showed Bush’s weakness on taxes and the economy. Buchanan went on to win only 18 delegates, but they earned him a speaking slot at the convention. Bush then lost to Bill Clinton in the general election.

Two recent national polls show that Trump’s challengers are all polling at 3% or less.

So Trump seems to be mostly ignoring them. Sort of. “I guess it’s a publicity stunt,” he said last week. “So, to be honest, I’m not looking to give them any credibility. They have no credibility.”

Trump has said he had nothing to do with the effort to cancel nomination contests in key states next year.

Without a presidential preference primary, the unbound delegates could come back to haunt Trump in a worst-case scenario.

“They are basically free agents,” said Elaine Kamarck, a Brookings Institution fellow and expert in primary politics.

“The more untethered delegates, the easier it is to break open a convention,” she said.

That’s exactly why anti-Trump activists in Colorado moved to cancel that state’s GOP primary in 2016, instead sending unpledged delegates to the Cleveland convention. Some of those delegates played a role in a short-lived attempt to derail Trump’s nomination on the opening day.

Once a party insurgent, Trump now has all the benefits of incumbency and appears focused on the general election. He has not campaigned in Iowa, and made one official visit to New Hampshire last month.

Trump’s three Republican challengers have different strategies for dealing with the canceled primaries. Walsh says he’s redoubling efforts in the states without primaries.

“We’re going to campaign in South Carolina, Arizona, Nevada, and Kansas, because I believe if we let these Republican voters know that the president of the United States just took away their right to vote, they’ll march on the headquarters of their state parties to get that right to vote back,” he told CNN Monday.

Weld is focusing on 20 states with open primaries — meaning independents and sometimes even Democrats can switch parties. He’s hoping that retail-level politics and his appeal as a moderate can win crossover voters in places like New Hampshire.

“I can campaign there as many days a week as I want, and always sleep in my own bed,” Weld said from Boston on Wednesday. “I don’t think Mr. Trump has an appetite for retail-level campaigning in New Hampshire. He’ll probably hold a few rallies and shake a few hands and leave it at that.”

His argument to Democrats: “They can try to guess who’s the strongest Democrat. But if they want to vote against Trump they can cross over and vote against Trump.”