Nikki Haley Is Running for President, the First G.O.P. Rival to Take On Trump

CHARLESTON, S.C. — Nikki Haley, the former South Carolina governor and United Nations ambassador, officially entered the race for president on Tuesday, a well hinted-at move that is likely to leave her the lone formal Republican challenger to former President Donald J. Trump for many weeks, if not months, as other potential 2024 rivals bide their time.

By announcing early, Ms. Haley, 51, who has spoken of the need for “generational change” in her party, seized an opportunity for a head start on fund-raising and to command a closer look from potential Republican primary voters, whose support she needs if she is to rise from low single digits in early polls of the G.O.P. field.

She made the announcement in a video.

This is a developing story and will be updated.