Nearly 20 years after President Bill Clinton declared that “the era of big government is over,” Hillary Rodham Clinton is proposing muscular federal policies that would require hundreds of billions of dollars in new spending and markedly expand Washington’s influence in a host of areas, from universal prekindergarten to Alzheimer’s disease research.

Her presidential campaign has said little yet about the costs of her policy ideas or how she would pay for them, but Mrs. Clinton is calling for government activism on a scale that she has not sought since her failed health care initiative in 1993 and 1994. But if her liberalism was seen as out in front of where many Democrats were then, she now seems to be catching up to the mood of the party.

“It’s not that the philosophical fights in the party between the left and the center have been settled in favor of big government,” said the presidential historian Robert Dallek. “It’s that likely Democratic primary voters right now want to see government used to build the economy.”

As ambitious as that may sound, Mrs. Clinton’s agenda may not be enough to satisfy restive liberals, including those supporting Senator Bernie Sanders of Vermont, who still suspect that she is not one of them. Nor is it likely to win many converts among the Republicans who control both houses of Congress and give her ideas (and Mr. Sanders’s) little chance of gaining traction there.