Senate Minority Leader Charles E. Schumer said Tuesday that he’s going to vote against Mike Pompeo to be secretary of state in part because he wouldn’t promise to publicly oppose firing of those leading the special counsel’s Russia investigation.

Mr. Schumer said he met with Mr. Pompeo and asked him to make a public statement defying Mr. Trump, but the nominee “demurred.”

Mr. Schumer said he also wanted Mr. Pompeo to issue public retractions of some past statements that the Democratic leader said could tarnish a new State Department secretary’s standing.

When Mr. Pompeo wouldn’t commit to either of those steps, he lost the New York Democrat’s vote.

“I’m going to oppose the nomination,” Mr. Schumer said.

Despite Mr. Schumer’s opposition, Mr. Pompeo appears to have the votes needed to gain confirmation when the full Senate votes, perhaps later this week.