Most governors love the limelight during an election season, but Mr. Northam may have helped himself this year by quietly tending to alliances and candidates and largely letting events play out rather than be seen as trying to stage manage them. And by all appearances he seemed fine letting other politicians cut a bigger figure on the campaign trail.

Mr. Northam did appear at get-out-the-vote rallies in the final weeks before Election Day, and at two dozen political events over the summer. But his predecessor, Terry McAuliffe, who in the spring ended a flirtation with a presidential run, was far more visible on the campaign trail. Mr. McAuliffe’s boisterous glad-handing was the opposite of Mr. Northam’s measured reserve. The former governor popped up at more than 125 parades and political events for candidates, sparking rumors that he might run again for governor in 2021. (Mr. Northam will be ineligible because Virginia governors cannot serve back-to-back terms.)

While Mr. Northam’s political action committee raised $1.5 million for Democrats on the ballot, it was a more modest sum than the $7.1 million that Mr. McAuliffe raked in for legislative races four years ago.

“What brought people to the polls on Tuesday, it was to vote for Governor Northam’s agenda,” said Jennifer Carroll Foy , a member of the House of Delegates. “I believe that no one wants to get in the way of what he can do here in Virginia.’’

In the end, money was no problem: It rained down on Democrats from national anti-gun and abortion rights groups, and from individual donors in the state and around the country. All were driven to flip the General Assembly, where Republicans’ narrow majorities were the last barrier to unified Democratic control of state government for the first time in 26 years.

Party officials and analysts in Virginia said Mr. Northam owed his political survival to fortuitous events as well as his own efforts.