Senator Dean Heller on Wednesday called President Trump “a great leader” who had revived Nevada’s economy, a striking departure from the arm’s-length approach Mr. Heller took with Mr. Trump in the 2016 campaign and in the first months of his presidency.

In a private conference call with White House aides, other Nevada Republican officials and local activists, Mr. Heller — the most endangered Senate Republican up for re-election this November — offered an unqualified embrace of the president.

“Our arms are wide open,” Mr. Heller said on the call, held to drum up interest in Mr. Trump’s campaign rally scheduled for Thursday in Las Vegas. “We’re so thrilled to have the president.”

Mr. Heller has steadily moved closer to Mr. Trump, finally acknowledging last year that he voted for the president, but the senator has not gone as far in public as he did Wednesday. Mr. Heller memorably said in October 2016, weeks before the presidential election, that he was “100 percent against Clinton, 99 percent against Trump.”