But Mr. Steyer began informing aides early this week that he would not be a candidate after all, after concluding that he could have a greater political impact through his impeachment activism, several advisers to Mr. Steyer said. Mr. Steyer intends to spend at least $40 million on impeachment efforts in the coming year — money that might otherwise have been directed toward a campaign for the Democratic presidential nomination.

“Most people come to Iowa around this time to announce a campaign for president,” Mr. Steyer said in prepared remarks, which were obtained by The New York Times. “But I am proud to be here to announce that I will do whatever it takes, for as long as it takes, to remove a president.”…

An adviser to Mr. Steyer, who requested anonymity to discuss private conversations with him, said that he had been unruffled by Ms. Warren’s attacks on billionaire candidates. But, the adviser said, Mr. Steyer was impressed by Ms. Warren’s rollout as a candidate and suggested that her announcement video channeled the very themes he had been planning to campaign on.