Virginia Gov.-elect Ralph Northam. (Salwan Georges/The Washington Post)

Virginia Democrats are giddy. And a bit put out.

Fresh off their second consecutive sweep of the state’s top three state offices, they could also secure a 50-50 split with Republicans in the House of Delegates … if random chance in the 94th district race breaks a tie in their favor.

Now, surely, the great causes Democrats have long championed in the house to no avail — be it school funding, climate change or health care — finally can move from campaign brochures to enacted legislation.

And woe to any who stand in their way after 17 long years in the political wilderness.

That includes you, Ralph Northam.

In an interview with The Post’s Gregory Schneider, Northam, the governor-elect, sounded the low-key, bipartisan tones that have marked his political career.

Northam will not be storming any barricades or scaling any scary political heights. Rather, Northam said he would avoid “showboating” and is urging new Democratic House members to forge relationships with Republicans.

Northam also said he wasn’t interested in imitating former governor Jim Gilmore, who tipped the General Assembly’s partisan balance to favor Republicans by offering plum state posts to incumbent Democratic lawmakers.

And Northam also soft-peddled Medicaid expansion, warning of the program’s rising costs and the need to contain them.

It was Northam at his best — conciliatory, comforting, professional.

Progressives went ballistic.

Tom Perriello, whom Northam walloped in the Democratic primary in June, demanded a vote on expansion before the 2019 elections, casting expansion as “a policy that is morally right & good for VA economy.”

Others criticized Northam for “taking the high road” and much more.

They want Northam to be like Gilmore. And they want him to do it now.

Progressives are impatient to expand state power while they feel they have the political wind at their backs. Gilmore never let niceties such as political healing get in the way of his agenda, so why should Northam (who had to walk back his Medicaid statements soon after the criticism erupted) be any different?

That goes double when we consider that wave elections are rare events, and some Democratic House victories were by such narrow margins that Republicans could easily flip the House back to their full control in 2019.

The Northam-progressive tiff got a bit of outside mediation when Gov. Terry McAuliffe (D) put Medicaid expansion at the heart of his final proposed state budget.

Northam devoted the final paragraph of his release to say that he remains “fully committed” to expansion and, picking up Perriello’s criticism of his earlier remarks, said that “Virginians elected us all to put politics aside and do what is right — expanding Medicaid should be at the top of the list this session.”

The progressive yelp had some effect.

But sharing power means compromise.

Compromise would seem to indicate that a straight up-or-down vote on Medicaid expansion isn’t possible. Republicans will never go for it, and in the event of a tie vote, legislation expanding Medicaid would die.

Bu 20 years ago, Gilmore got his legislative priority — car tax repeal — through an equally divided House as part of the state’s budget.

He got a helping hand from his predecessor, George Allen, who built his final budget proposal around car tax repeal.

So there is close precedent then, for an incoming governor riding a big win to get an even bigger new program through an equally divided House in a budget year.

Except Republicans controlled the Senate in 1997 thanks to Gilmore’s appointment of Democratic Sen. Charles Waddell to his cabinet and a Republican victory in the subsequent special election to fill the seat.

To get the Medicaid expansion he says he wants, Northam may yet come around on the progressive criticism of refusing to embrace the Gilmore playbook and pick a Republican or two looking for a nice state job with a great pension to close out their careers.

Maybe. But he should read the rest of the Gilmore script before he does, and realize that supposedly friendly majorities can turn implacably hostile, putting his party’s electoral fortunes and his big policy issue at risk.