None of the president’s economic initiatives, however, represent a departure for Mr. Obama himself, or for his party. If President Bill Clinton set out to build a “bridge to the 21st century,” said Simon Rosenberg, the president and founder of the New Democrat Network, Mr. Obama is walking across it.

John D. Podesta, an Obama adviser who served as chief of staff in the Clinton White House, called the president’s second-term economic agenda “consistent with where he’s been, consistent with where Clinton was.”

Indeed, since World War II both parties have accepted a substantial measure of federal activism “as American as apple pie,” said Kenneth Baer, a former Obama budget aide.

Mr. Obama’s problem is that postwar America could afford more pie than a post-baby-boomer America will be able to. And in the era of the Tea Party, Republicans have proved increasingly willing to challenge once-settled assumptions about Washington’s role.