Even moderate Democrats took notice.

“If you take what the left side of that debate was and the more moderate side of the debate, both positions — the whole range of positions — are significantly more progressive than where we were just seven or eight years ago,” said Ronald Klain, an aide to former Vice President Joseph R. Biden Jr. and a senior adviser to his presidential campaign, in a television interview last week.

With five weeks to go until the next debates, and six months until the Iowa caucuses kick off voting for the 2020 nominee, the Sunrise activists have strategy decisions to make about how to keep their influence going. In August, typically considered a sleepy month in the presidential cycle, Sunrise leaders said they planned to fill that vacuum with new ways of pressuring the presidential contenders, though the specific ways are yet to be decided.

The two candidates most popular with liberal activists and voters, Senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, are in the top tier of the Democratic primary race, according to polling. But neither has overtaken Mr. Biden, who continues to benefit from a perception among many voters that he is best suited to beat President Trump. Among the questions that the activists are pondering: Should they concentrate their support on Mr. Sanders or Ms. Warren? Or should they further push their policy ideas among the entire field, trying to ensure that any nominee, including Mr. Biden, enters the general election with the most liberal platform possible?

The answer is both, the group’s leaders said.

“Our job isn’t to be nice,” said Alexandra Rojas, the executive director of Justice Democrats, the progressive group that has roiled Washington by challenging more centrist congressional Democrats from the left.