WASHINGTON — Their previous jobs have taken them to the Oval Office, the Situation Room and the Senate floor. One met with a Saudi king and plotted strategy to fight the Islamic State. Another cracked down on human rights abuses in North Korea. Their Rolodexes are flush with former cabinet members and current Pentagon officials who are happy to take their calls.

Nearly a dozen members of the House’s incoming class are far from being gawky freshmen, stumbling wide-eyed through the strange corridors of Capitol Hill, but are instead experienced policymakers who have worked in previous presidential administrations — seven of them for former President Barack Obama. Their return to Washington is, in part, a way to undo what they see as the unspooling of the values and legacy of the nation’s 44th president.

“We have just won a very fragile foothold in one institution in Washington at a time when all the institutions and norms are under attack,” said Tom Malinowski, who served Mr. Obama as assistant secretary of state for democracy, human rights and labor. “This election is not about changing the country. It’s about saving the country.”

But in a freshman class where confrontation, not cooperation, could be most prized, it is not clear whether the Washington veterans will assume leadership roles or take a back seat to younger, brasher freshmen like Alexandria Ocasio-Cortez of New York and Ilhan Omar of Minnesota.