The Democrats are jubilant. In elections Tuesday, no congressional seats were up for grabs, but the blue party scored splendidly in state and local contests, so much so that to hear them talk you would think they had parted the populist red sea.

Their big prize was victories in two gubernatorial races that they were expected to win anyway. They took traditionally liberal New Jersey by the same wide margin that polls predicted. They triumphed in Virginia, which had gone Democratic the last three presidential elections. But they won the state by six more points than expected. Their voters showed up in droves, they crowed, even in the rain and cold.

The party also made big gains in the Virginia legislature and took control of the Senate in Washington State. It captured several mayoralties, did very well in suburban areas, seizing county executive offices in states like New York.

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Lest progressives get too excited, some qualifiers. The wins were down-ballot. They came against a sitting Republican President holding the lowest approval rating in year one in recorded history. They were registered primarily on Democratic or neutral turf, which provided the party with a built-in advantage going in. And in off-year elections, it's normal for the opposition party to score well anyway.

But while many of their advances, as polling expert Nate Silver contends, were predictable, it was still a banner day for the Democrats. If the results didn't portend that populism is on the wane, that "a blue wave is building," as Maryland party chair Kathleen Matthews gloated, the wins unburdened the Democrats of the tag of being "a party in disarray."

The disarray cliché certainly looked to have credence. The Democrats' fundraising has been meagre, they'd lost four special elections for House seats to the Republicans this year and there was infighting between their moderate and progressive wings. The party was still embittered by Hillary Clinton's defeat, and former party interim chairwoman Donna Brazile had just published a disparaging inside-look book.

The gloom was palpable. But as is often the case with parties in opposition, it's not so much what they are doing that counts, but the incumbents. Tuesday's tests, Republican congressman Scott Taylor said, became a referendum on the performance of U.S. President Donald Trump. That was enough to scare up the Democratic triumphs.

Predictably Mr. Trump didn't see it that way. In reference to the defeat of Virginia gubernatorial candidate Ed Gillespie, he tweeted that he lost for "not embracing me and what I stand for." In fact, Mr. Gillespie did tie himself to the Trump agenda in the campaign's final days, to no avail.

A CNN poll taken over the last few days asked voters if they thought Mr. Trump deserved re-election. Sixty-three per cent said no. Of that nearly-two-thirds figure, large numbers were angered enough at this President to get out and vote. Swing voters, many of them moderate-leaning suburbanites who went Republican last November, returned to the Democratic fold.

Republicans like House Speaker Paul Ryan placed the electoral setback on the Grand Old Party's failure to deliver on campaign promises, adding that passing tax reform was now crucial. Exit polls showed the Republicans, having failed to bring in a replacement for Obamacare, were hurt badly by the health-care issue.

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The message from Tuesday, said Republican senator Jeff Flake, a harsh Trump critic, is that the GOP has to expand the tent. "We've seen the limits on how far we can drill down on the base."

The question is whether the local and state results are harbingers of voting at the national level in midterm elections a year from now. In recent times they have indeed been prescient, and if Mr. Trump doesn't respond to this wake-up call and change course, he could face dire consequences. Midterm elections are often nightmares for incumbents. Barack Obama, George W. Bush and Bill Clinton all suffered devastating midterm repudiations.

The large number of state and local wins on Tuesday have distanced the Democrats from the Clinton collapse, invigorated the party and demonstrated that right-side populism, owing to Donald Trump's ineptitude, could well be a passing phase.