WASHINGTON — Nearly three weeks after Election Day, Hillary Clinton’s campaign said on Saturday that it would participate in a recount process in Wisconsin incited by a third-party candidate and would join any potential recounts in two other closely contested states, Pennsylvania and Michigan.

The Clinton campaign held out little hope of success in any of the three states, and said it had seen no “actionable evidence” of vote hacking that might taint the results or otherwise provide new grounds for challenging Donald J. Trump’s victory. But it suggested it was going along with the recount effort to assure supporters that it was doing everything possible to verify that hacking by Russia or other irregularities had not affected the results.

In a post on Medium, Marc Elias, the Clinton team’s general counsel, said the campaign would take part in the Wisconsin recount being set off by Jill Stein, the Green Party candidate, and would also participate if Ms. Stein made good on her plans to seek recounts in Michigan and Pennsylvania. Mrs. Clinton lost those three states by a total of little more than 100,000 votes, sealing her Electoral College defeat by Mr. Trump.

The Clinton campaign had assailed Mr. Trump during the election for refusing to say he would abide by the results if he lost. On Saturday, Mr. Trump responded to the campaign’s decision to join the recount with a statement calling the effort “ridiculous” and “a scam by the Green Party.”