What was Ukrainian President Volodymyr Zelensky doing at what sure looked like a partisan US political event this week?

And how did the White House let this happen?

Zelensky got flown into battleground Pennsylvania aboard a USAF C-17 plane on Tuesday; he then toured the Scranton Army Ammunition Plant accompanied by Gov. Josh Shapiro, Sen. Bob Casey, Rep. Matt Cartwright — the last two being active Democratic candidates.

And it looks like no GOP candidates got invited — trapping a foreign head of state into apparently taking sides in US domestic politics.

Yet Zelensky was guarded by Secret Service agents and driven around in Secret Service vehicles, adding more reek of impropriety: Who covered those expenses?

Someone in the Biden administration pulled a fast one: Pennsylvania has a fair number of anti-Russian Polish-Americans and others of Eastern European heritage who might be swayed by Zelensky’s seeming preference.

Legalities aside, this is terrible for Zelensky: Ukraine desperately needs support from Republicans as well as Democrats in Congress, and will no matter who holds the White House next year.

House Speaker Mike Johnson is calling on Zelensky to fire his US ambassador for letting this disgrace happen, a move that could mend Ukraine’s fences here.

But Congress will need answers on the American side, too: After all, Democrats impeached President Donald Trump over his supposed abuses linked to Ukraine; now we have the misuse of a foreign guest’s visit to influence US politics.

We absolutely endorse US support of Kyiv against Moscow’s brutal invasion: Vladimir Putin must not succeed.

And Democratic candidates have every right to slam those Republicans who want to hang Ukraine out to dry.

But dragging any foreign leader, especially one who’s seeking now new support for his nation from the White House, into US politics is morally criminal — at least.

Whether at the White House or the State Department, American heads need to roll over this.