What does Trump have riding on the Pennsylvania special election? Both Saccone and Lamb have spoken favorably about Trump’s proposal to impose tariffs on steel and aluminum imports from certain countries, an idea that congressional Republicans have broadly rejected. And the president is going to Pennsylvania to campaign for the Republican candidate on Saturday. A Saccone win could help Trump politically and in terms of policy — showing that the president can boost a GOP congressional candidate in a key race and that one of his more unorthodox policy ideas (the tariffs) perhaps doesn’t hurt the party’s electoral chances.

But if Saccone loses, it would be the second special election in three months in which Trump campaigned hard for a GOP candidate only for him to lose. A few days before the December election in Alabama, Trump held a rally in Pensacola, Florida — less than 20 miles from the Alabama state line — and strongly urged voters to back GOP Senate hopeful Roy Moore. We all know how that turned out.