Hard to say what Tuesday’s election will mean for 2018

During a pre-election stop in Pittsburgh the weekend before the election, Democratic National Committee vice-chairman Michael Blake said the outcome Nov. 7 “will demonstrate what is the momentum on the ground against Trump. … And it will give us guidance about what kind of races to run in 2018.”

The guidance, pundits agreed before all the ballots were even counted, was that voters in affluent suburbs were revolting against Mr. Trump. Suburbanites in Northern Virginia blasted GOP gubernatorial candidate Ed Gillespie.

In Philadelphia’s suburbs, “Republicans are doing what Democrats have been doing in the southwest: either changing their registration or voting outside their party,” said Franklin & Marshall College pollster Terry Madonna. While that trend has long been underway among the area’s more moderate voters, he said, “Anti-Trump sentiment is accelerating it.”

“Trumpis very weak and gettingweaker in affluent areaswith high levels of educational attraction,” agreed KyleKondik, who studies andpredicts election trends atthe University of Virginia Centerfor Politics. But Mr. Gillespiedid well in more Appalachianparts of that state, hesaid, adding that “Western Pennsylvaniais Appalachian too,and it’s been trending Republicanfor years.”

Mr.Kondik said a better gaugefor political sentiment herewould be the battle to replaceMr. Murphy, whose districthas above-average incomeand educational levels. “Republicansare strongly favored to hold it. But if there’s considerableerosion in GOP performance,that will tell us moreabout Western Pennsylvania.”

Judicial races, after all, often fail to predict future results. In 2015, Democrats swept all the statewide judicial races on the ballot — and then went on to suffer crushing losses in the race for president and Senate the next year.

As for this year’s Supreme Court race, many Democrats privately conceded it months ago: Judge Woodruff struggled with fundraising and a low-visibility ground game. Despite having earned a Super Bowl ring as a Steeler, he lost every southwestern Pennsylvania county except Allegheny. Ms. Mills ascribed that outcome to a late-breaking Republican ad accusing the judge of nepotism.

Further down-ballot, the tea leaves are harder to read. Democrats won three of four Superior Court seats and split a pair of Commonwealth Court seats with Republicans. At the municipal level, Democrats won two key races in Erie. But Democratic County Executive Kathy Dahlkemper beat her rival by less than half a percentage point. Erie mayoral candidate Joe Schember’s less than 7-point win over John Persinger was comparatively tight in a staunchly Democratic city.

Once reliably Democratic, Erie County backed Donald Trump in 2016, a reversal that put a dagger through Hillary Clinton’s chances. Even with a solid base in the southeast, that may be a concern for the reelection chances of Gov. Tom Wolf and Sen. Bob Casey next year.

Mr. Casey has long opposed the trade deals that Mr. Trump also campaigned against last year, and “he should have strong legs to stand on” next year, said Andrew Bloeser, a political science professor at Allegheny College not far from Erie County. “Erie is becoming more competitive, but I don’t know that it’s turning red.”

“If people are concerned that [Mr. Trump’s] bluster has done nothing for their economic concerns, that may not bode well for him or those down ballot” next year, he said.

Still, polling suggests that Mr. Trump is, at least for now, mostly holding on to his white working-class base. And while Republicans elsewhere may fret about his impact on 2018, Mr. Raja said that even after Tuesday, “I’m still hearing a very much pro-Trump message.”