Republican leaders in Nevada, South Carolina and Kansas have voted to scrap their presidential nominating contests in 2020, erecting more hurdles for the long-shot candidates challenging President Trump.

“What is Donald Trump afraid of?” asked one of those rivals, former Massachusetts Gov. Bill Weld.

Canceling primaries, caucuses and other voting is not unusual for the party of the White House incumbent seeking a second term. Doing so allows Trump to try to consolidate his support as Democrats work to winnow their large field of candidates.

A spokesman for the South Carolina Republican Party, Joe Jackson, confirmed that the state party voted Saturday against holding a presidential primary next year.

A similar move followed in Nevada, where party spokesman Keith Schipper said, “The vote to opt out of the caucus has passed. We will vote to endorse and bind the delegates to the president at a later date.”

In Kansas, the state GOP tweeted on Friday that it will not organize a caucus “because President Trump is an elected incumbent from the Republican Party.” Its state committee planned to approve rules for an “internal party process” for selecting convention delegates, according to Kelly Arnold, the party’s former state chairman, and Helen Van Etten, a member of the Republican National Committee.

Challengers have emerged to Trump, including Weld and Joe Walsh, a one-term Illinois congressman, and Mark Sanford, the former South Carolina governor and congressman, who joined the race on Sunday.

Weld, in a statement, said voting is “the ultimate right of speech in America, and Trump’s machine in South Carolina has just told the people of South Carolina that they don’t need to be heard. Donald Trump wants to be treated as a monarch, but we rejected that idea 200 years ago.”

Walsh told CNN after the South Carolina vote that his campaign would “fight South Carolina and any other state that considers doing this.” He also noted that Trump complained during the 2016 election “about how the Democrats were rigging the system to get Hillary [Clinton] elected. Well, look what he’s doing now. You talk about rigging a system.”

Primary challenges to incumbents are rarely successful, and Trump’s poll numbers among Republican voters have proved resilient. Nonetheless, Trump aides are looking to prevent a repeat of the convention discord that highlighted the electoral weaknesses of Presidents George H.W. Bush and Jimmy Carter in their failed reelection campaigns.

“As the chairman of the Nevada Republican Party, my job is to ensure not only President Trump’s victory in Nevada, but also to elect more Republicans down the ballot,” state party Chairman Michael McDonald said. “It would be malpractice on my part to waste money on a caucus to come to the inevitable conclusion that President Trump will be getting all our delegates in Charlotte. I am excited that our central committee has agreed with this proposal and voted to give us a way to bypass the caucus process.”

Since last year, Trump’s campaign has worked to monitor and at times control the process by which delegates to next year’s Republican National Convention in Charlotte are selected. His campaign wants the convention to be a four-night “infomercial” for Trump by sidelining the president’s detractors within the party.

The effort is an acknowledgment that Trump hasn’t completely cemented his grip on the GOP and might not coast to the nomination without some opposition. To that end, the campaign has worked over the past year to scuttle any attempts at a Trump challenge by party dissidents, mindful that a serious primary opponent could weaken Trump heading into the general election.

In January, the Republican National Committee voted to express its “undivided support” for Trump and his “effective presidency.”

In years past, both Republicans and Democrats have cut state nominating contests when an incumbent president from their party ran for a second term. In 1984, South Carolina GOP leaders opted to call off their primary as President Reagan sought a second term. In 2004, the GOP again canceled the state’s primary with leaders deciding instead to endorse President George W. Bush’s reelection bid.

The South Carolina Democratic Party didn’t hold presidential primaries in 1996 or in 2012, when Presidents Clinton and Obama were their incumbents.

Associated Press writers Michelle Price in Las Vegas, Jonathan Cooper in Phoenix and John Hanna in Topeka, Kansas, contributed to this report.