[Which Democrats are leading the 2020 presidential race this week?]
Bill Stepien, a senior political adviser to the president, Mr. Clark and other campaign officials have spent most of this year working with state Republican officials either to change rules or to push for party chairs who are favorable to Mr. Trump.
Republican parties in states like Massachusetts — a blue state that is nonetheless delegate-rich at party conventions because of its large population — have changed their rules so that any candidate who wins more than 50 percent of the vote in the primary captures all the delegates.
New York, the president’s home state and another with a large population, has a new Republican Party chairman, Nick Langworthy, who is viewed favorably by the national committee and the White House. There, too, the rules now allow for a winner-take-all delegate award if a candidate clears 50 percent of the vote.
Republicans are trying to avoid the conflicts that arose at conventions such as the one in 1992, when Patrick J. Buchanan challenged the incumbent Republican president, George Bush, for the nomination. Mr. Buchanan didn’t gather significant support in most of the primaries. But he rolled into the party’s convention at the Astrodome in Houston with enough support to draw cheers during a thunderous speech about the “culture war” being waged for the soul of the nation.
In 1976, President Gerald Ford faced a nominating challenge from Ronald Reagan. The incumbent found himself wooing delegates to lock them up at the convention, using enticements like offering rides aboard Air Force One.
For both Mr. Bush and Mr. Ford, the primary challenges helped expose weaknesses that were exploited in the general election. Despite Mr. Trump’s high popularity in polls of Republican voters, his campaign is seeking to avoid any signs of discord. That includes a situation like the one Mitt Romney faced in 2012, when he was forced to contend with changes sought by delegates supporting Ron Paul.
There are other measures the Trump team has taken. Four states have canceled their primaries, including South Carolina, in moves that will further prevent his challengers — the former congressmen Joe Walsh and Mark Sanford, and the former Massachusetts governor William Weld — from gaining traction.