President Trump tries to fire up the crowd at a rally for Republican Rick Saccone in Moon Township, Pa., on Saturday. Saccone is running against Democrat Conor Lamb in Tuesday’s special election for the congressional district vacated by Republican Tim Murphy. (Keith Srakocic/AP)

It’s almost certainly not a coincidence that President Trump decided to announce new tariffs on steel imports shortly before Tuesday’s special election in southwestern Pennsylvania. The area, near Pittsburgh, is part of the Rust Belt, theoretically the sort of blue-collar industrial area that Trump sees as central to his political base. There was some speculation that Trump was announcing his planned tariffs only to boost Republican candidate Rick Saccone’s chances in Pennsylvania’s 18th Congressional District; either way, it’s clear that Trump saw the tariffs as something that would appeal to voters there.

“A lot of steel mills are now opening up because of what I did,” the president said of his introduction of tariffs. This is certainly a questionable claim.

But, more broadly, it’s questionable as a sales pitch. When Trump announced last year that he was withdrawing the United States from the Paris climate agreement, he said he was doing so because he was defending Pittsburgh, not Paris. It was a reminder that he sees Pittsburgh and the broader area around the city as though nothing had changed since the late 1970s. At the time of the announcement, we noted that manufacturing jobs in the region pale next to jobs in, for example, health care or renewable energy. Trump is making a sales pitch to a southwestern Pennsylvania that largely no longer exists.

It shouldn’t be a surprise, then, that the sales pitch didn’t really work. A new poll in the 18th District from Monmouth University shows that Democrat Conor Lamb has a slight lead over Saccone and that Trump’s tariffs announcement didn’t do much to change that.

More people in the district think the tariff announcement will help the region rather than hurt it, Monmouth found. But the combined percentage saying the tariffs would either hurt or have no effect on the local economy was larger than the percentage who said the tariffs would help. In Allegheny County, home to Pittsburgh (which is outside the district), support for the tariffs is lower than in other parts of the district.

There is a predictable partisan split there, with 15 percent of Democrats saying the tariffs will help. But Lamb pulls more support from Republicans (9 percent) than Saccone does from Democrats (5 percent) — suggesting that Democrats who approve of the tariffs aren’t then persuaded to back Saccone.

Monmouth asked about that directly. Nearly everyone — Democrat, Republican, independent — said the tariffs announcement had no effect on how they planned to vote.

About 5 percent of independents said it made them more likely to vote for Saccone, which is about as close to good news for Trump as the poll shows. Nearly everyone else, though? Shrugs.

The broader problem for Trump, of course, is that the tariff play has such a limited audience among voters that it doesn’t even land in the place that he seems to envision as the most appreciative. It is as though he declared that the New England Patriots were now illegal and he didn’t pick up any votes in Philadelphia.

Except that it is more like he said the Denver Broncos were illegal and he picked up no votes in Tallahassee, because Tallahassee isn’t really that worried about the Broncos. According to the Census Bureau, about 10.3 percent of jobs in the 18th District were in manufacturing from 2012 to 2016. The average across all congressional districts was 10.4 percent.

Trump’s pitch for tariffs was politically as much about appealing to the nostalgia of a bygone blue-collar America as it was about specifically trying to reopen steel plants in Pennsylvania. As an effort to prove to the 18th District that he might revive the economics of that era, Monmouth’s polling suggests it failed.