Former President Donald J. Trump glided to victory in Nevada’s Republican caucuses on Thursday, an outcome all but guaranteed because he was the only major candidate on the ballot.

The Associated Press declared Mr. Trump the winner shortly after caucus sites closed in Nevada, giving him his fourth straight triumph in a Republican nominating contest that awards delegates this year.

Even in a campaign in which Mr. Trump’s dominance has sapped the race of much of its drama, his win in Nevada felt particularly preordained. His last significant G.O.P. rival, Nikki Haley, opted months ago to skip the caucuses, which were run by the Nevada Republican Party, and participated instead in a primary election on Tuesday required by state law.

Embarrassingly for Ms. Haley, she was heavily outvoted in that election by a “None of These Candidates” option on the ballot. She was essentially unopposed, but even without Mr. Trump on the ballot, Republican voters rejected her.

Ms. Haley still won the contest, but its results were effectively immaterial. The state’s Republican Party, which is led by a close Trump ally, decided that it would allocate its presidential delegates based only on the caucuses, and it forced candidates to choose to participate in one contest or the other.