COLUMBIA, S.C. — Republicans in South Carolina, Kansas and Nevada scheduled meetings Saturday to decide whether to scrap presidential preference contests before the 2020 election, which would not be an unusual move for the party of the White House incumbent seeking a second term. Still, it would put up even more obstacles for the long shots challenging President Trump in 2020.

At stake were GOP primaries, caucuses or other voting in those states next year. A decision by party officials in Arizona is expected later in the month.

Challengers have emerged to Trump, including Bill Weld, a former Massachusetts governor, and Joe Walsh , a former Illinois congressman. Others may join them.

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.

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, North Carolina, 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 Republican party 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 Republican leaders opted to call off their primary as President Ronald Reagan sought a second term. In 2004, the party 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 Bill Clinton and Barack Obama faced no opposition for second terms.

South Carolina GOP leaders expected to announce their decision midday Saturday. In Kansas, the Republican Party’s state committee was expected to approve rules Saturday for an “internal party process” for selecting delegates to the national convention without caucuses, according to Kelly Arnold, the party’s former state chairman, and Helen Van Etten, a member of the Republican National Committee from Topeka.

The Nevada Republican Party was expected to hold a vote later Saturday on possibly changing its rules to allow a bypass of its presidential nominating caucuses in 2020 and endorse Trump outright. The move would allow the state’s central committee members to hold a vote and commit the state’s GOP delegates to the president, shielding him from a primary challenge.

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