The promise and limits of the Democratic turnout machine were on display in November 2013. In the Virginia governor’s race, Terry McAuliffe’s well-funded campaign resurrected elements of the Obama campaign’s turnout apparatus in a contest against an underfunded challenger, Ken Cuccinelli, who alienated many of the state’s socially liberal voters. As a result, Mr. McAuliffe held a significant lead in the polls, even among likely voters.

But on Election Day, Mr. McAuliffe won by only 2.5 percentage points, less than Mr. Obama’s 3.9-point margin in November 2012, even though Mr. McAuliffe clearly outperformed Mr. Obama in Northern Virginia among the state’s moderate, affluent swing voters.

The problem was lower Democratic turnout. The electorate more closely resembled 2009 than 2012, according to Harrison Kreisberg, who directed the Virginia operation for BlueLabs, a Democratic analytics firm founded by former Obama campaign operatives.

BlueLabs’s analysis showed that Mr. McAuliffe’s margin would have expanded by an additional 5 points if turnout had been equivalent to that of the 2012 race.

That analysis is consistent with the precinct-level results. Turnout fell by more than it did statewide in heavily Democratic precincts — usually with an overwhelmingly African-American population. The decline wasn’t as steep as in 2009, but it could not be mistaken for the 2012 electorate either.

This doesn’t mean the Democratic turnout operation was ineffective. It helped on the margins. After all, the Virginia electorate was more favorable for Democrats in 2013 than it was in 2009.

But Mr. McAuliffe’s win was narrow — especially considering the tepid Republican effort. And no Democratic turnout effort will revitalize the so-called Obama coalition of young and nonwhite voters in an off-year election. The levels of voter interest in a midterm election and presidential election are simply too different. Indeed, Mr. Kreisberg said the McAuliffe campaign didn’t aim to match 2012 turnout; it was mainly focused on outperforming turnout in 2009.