Democrats had better appeal to voters in the center

— only more so. A Pew Research Center poll last month showed that voters on all sides are unusually focused on choosing which party controls Congress and making their votes a judgment on the president.

That’s bad news for Republicans. Despite occasional good weeks, Trump remains the most unpopular first-term president of modern times.

Democrats have the advantage of an “enthusiasm gap,” according to Pew, with self-described liberals especially fired up. But the Democratic lead on the question of which party voters prefer has ebbed from 13 points in January to 6 points today (46 percent to 40 percent) — not enough to ensure a change in control of Congress.

Those numbers at least should indicate to Democrats that they can stop worrying about their base — liberal and progressive voters plan to turn out. The key to winning back the House, veteran party strategists argue, is appealing to voters in the center.

“Keep the debate on issues that matter to swing voters,” advises Mark Mellman, who has worked for Sen. Heidi Heitkamp, D-N.D., and California’s Barbara Boxer. Don’t push a left-wing wish list — even after Democratic socialist Alexandria OcasioCortez’s primary win in New York City last month.

Swing voters care about the economy — not the Wall Street economy that’s booming, but the household economy where people say they haven’t felt much benefit from the GOP’s tax cut. Republican candidates are trumpeting good unemployment and growth numbers, and they’re praying that a new GDP measure due out July 27 will show a big jump.

But Democrats don’t need to concede the point. Polls show that the massive shift in taxation that Republicans passed last year is unpopular, an unusual achievement for a tax cut. In several recent polls, no more than 1 in 4 Americans said they had noticed any decrease in their tax bills.

“Trump is going to present the economy and the tax cuts as a success,” said Stanley Greenberg, another strategist. “We want that fight … . What’s killing people is rising costs: housing, health care, child care.”

Voters are particularly worried about health care: The Trump administration gave Democrats a powerful new talking point last month when it asked a federal judge to undo massively popular protections for people with pre-existing medical conditions.

Immigration isn’t an issue most Democrats in swing districts would have chosen to run on, but they can’t avoid it now. Calls from Ocasio-Cortez and other progressives to abolish Immigration and Customs Enforcement earned a gleeful response from Trump and other Republicans who want to tar the Democrats as soft on crime.

The raw politics of the issue is clear: If migrant families are still separated or caged in internment camps by November, Republicans will suffer at the ballot box. But if Trump can change the subject to “abolish ICE” and “open borders,” Democrats will pay a price.

Finally, Democratic candidates need to resist the temptation to react to everything Trump says, which lets him control the agenda, probably his greatest political talent. Resistance, as Mellman notes, will only get you so far in the midterms: “People do not lump every Republican with Trump.”

And unless special counsel Robert Mueller’s investigation reaches a clear conclusion before November, collusion is not going to decide the fall election.

A primary election win like Ocasio-Cortez’s doesn’t hold many lessons; her district is deep blue. What Democrats need most is wins in places such as Orange County, California, and the suburbs of Chicago or Philadelphia now held by GOP incumbents. Polls suggest a blue ripple, if not a wave, is reaching enough of those districts to give the Democrats a majority in the House.

The test of the next four months is whether Democrats will enlarge their lead or manage somehow to throw it away.