The group announced its plans in a memo on Tuesday.

The commitment by the network, Americans for Prosperity Action, bolsters Ms. Haley as the campaign enters the final seven weeks before the first nominating contest. Since the first Republican primary debate, Ms. Haley has steadily climbed in polls, and is closely competing with Mr. DeSantis for the second-place slot in Iowa. Former President Donald J. Trump remains the dominant front-runner in the race.

Ms. Haley, who has described Mr. Trump's time as past, has gained support from donors and her candidacy has received approval from elite opinion-makers, many of whom describe her as the best alternative to Mr. Trump.