Virginia Attorney General of Virginia Mark Herring, left, in October. (Astrid Riecken/For The Washington Post)

Virginia Attorney General Mark Herring declared Wednesday that he will not seek the Democratic nomination for the state’s top job in 2017, preferring instead to run for reelection. This is great news for Democratic Lt. Gov. Ralph Northam.

In Virginia’s two-party era, Herring’s early exit from the approaching gubernatorial election is unprecedented. At a similar point in their tenures, both Democrats Andrew Miller in 1973 and Mary Sue Terry in 1989 were still looking for a path to the gubernatorial nomination before deciding to run for reelection.

A recent poll found Herring leading Northam among Democrats by an overwhelming 33 percent to 9 percent for their party’s 2017 gubernatorial nomination. Democratic voters had a 33 percent to 13 percent favorable view of Herring but split 19 percent to 18 percent on Northam. The lieutenant governor, a Tidewater physician with an impressive résumé, announced his run for governor several months ago.

Why, then, did front-runner Herring make this historically early exit and concession, especially since the latest poll shows Northam trailing the strongest potential GOP nominee — 2014 Senate candidate Ed Gillespie — by 7 points ?

Herring’s statement provided no explanation. It focuses instead on why Herring deserved reelection. Miller and Terry won second terms with landslides. The only two lieutenant governors in modern times to seek reelection — Democrat Don Beyer in 1993 and Republican Bill Bolling in 2009 — each won handily. History, then, says Herring should be a heavy reelection favorite.

The most obvious explanation for Herring’s surprise decision: It is personal, outside the parameters of politics. Perhaps he doesn’t hunger for the power and pomp of the governorship. This would make him unique among modern attorneys general.

Making the run is no sure thing. Democratic Attorney General Jerry Baliles in 1985, Republican attorneys general Jim Gilmore (1997) and Robert F. McDonnell (2009) rode landslides into the governor’s office. But Democrats Miller in 1977 and Terry (1993) lost, as did Republican attorneys general Marshall Coleman in 1981, Mark Earley (2001), Jerry Kilgore (2005) and Ken Cuccinelli II (2013).

Gov. Terry McAuliffe (D) and Democratic power brokers deny pressuring Herring to drop out. But some well-connected Democrats had already talked publicly and privately about hoping to find a way to avoid a dragged-out nomination fight between Herring and Northam. They presumably are relieved.

The only fight between a sitting Democratic lieutenant governor and Democratic attorney general occurred in 1985 between Dick Davis and Baliles. The winner — Baliles — proceed to rack up the only Democratic gubernatorial landslide in the modern era, which also helped elect the state’s only African American lieutenant governor and female attorney general.

Perhaps the reason is simply this: Herring enjoys being attorney general. In Virginia, he can keep the job for life if the voters are willing.

But in Virginia politics, there is always the Machiavellian possibility.

Herring surely expects former secretary of state Hillary Clinton to be the next president. McAuliffe, one of her closest friends, would be in line for a major Cabinet post. If he resigns in early 2017, Northam becomes the incumbent governor. If Herring were running for the Democratic gubernatorial nomination, he would be in what the British call a “sticky wicket.”

Other Democrats would be running for attorney general, leaving Herring unable to seek reelection, stuck running against an incumbent Democratic governor. McAuliffe says he intends to serve out his term. But if a president and close friend says she needs him, would McAuliffe refuse?

Herring’s decision not to run, then, might be a smart move to prevent being left holding an empty political bag.

While Northam now seems a sure thing for the 2017 Democratic gubernatorial nomination, the rise of Bernie Sanders might offer a cautionary note. Democrats are not genetically endowed with the anointment and appointment gene, as former first lady Clinton is learning.

This leaves a final question: What to make of Northam running 7 points behind Republican Ed Gillespie in the most recent poll?

Gillespie, a former Virginia Republican Party chair, almost defeated Sen. Mark Warner (D-Va.) last year. This raises instant comparisons to 2001. Lacking any statewide officeholder, Democrats that year gave the gubernatorial nomination to former Virginia Democratic Party chair Mark Warner. Like Gillespie, Warner had been beaten several years before in a U.S. Senate race. As the saying goes, you know the rest of the story.

Herring is out. Northam wins, but so, for now, does Gillespie.