Ronna McDaniel, the R.N.C.’s Top Official, Plans to Step Down on March 8

The chairwoman of the Republican National Committee said on Monday that she would step down in just over a week, as former President Donald J. Trump seeks to install a new handpicked leader for the national party ahead of the general election this fall.

The decision is not a surprise. The chairwoman, Ronna McDaniel, told Mr. Trump weeks ago that she planned to leave shortly after the South Carolina primary, which was held on Saturday. But she now sets in motion a new election within the party’s official body, where Mr. Trump’s preference for chair and co-chair will try to secure enough votes to take over.

Mr. Trump has publicly backed Michael Whatley, the chairman of the North Carolina Republican Party and the national committee’s general counsel, to replace Ms. McDaniel. And he has said that he wants his daughter-in-law, Lara Trump, to be the next co-chair.

Mr. Trump’s remarks on the R.N.C. leadership came in the run-up to the South Carolina primary on Saturday, and in anticipation of his tightening his grip on the party. He ended up defeating his main rival, former Gov. Nikki Haley of South Carolina, by more than 20 points in her home state.

“I have decided to step aside at our spring training on March 8 in Houston to allow our nominee to select a chair of their choosing,” Ms. McDaniel said in a statement to The New York Times. “The R.N.C. has historically undergone change once we have a nominee, and it has always been my intention to honor that tradition. I remain committed to winning back the White House and electing Republicans up and down the ballot in November.”

Ms. McDaniel, the first woman chair of the R.N.C. in more than 40 years, thanked Mr. Trump and other Republicans for their support. She had been the chairwoman