Senator Chuck Schumer, the typically chatty New York Democrat and majority leader, often resorts to repeating a single terse phrase when he doesn’t want to answer a question.

“I’m with Joe,” was his mantra for two long weeks in July as he was barraged with questions about whether President Biden needed to withdraw from the presidential race after his devastating debate performance.

Mr. Schumer took the same approach on Tuesday as he tried to avoid passing judgment on the fraught subject of Mr. Biden’s full and unconditional pardon for his son Hunter.

“I’ve got nothing for you on that,” he told reporters at a news conference, repeating the statement three times in a row.

The awkward response reflected a painful reality that has begun to set in during the waning days of Mr. Biden’s term: His relationship with Democrats in Congress, which once served as the solid backbone of the party and his presidency, is badly frayed, and perhaps irreparably broken.

As Mr. Biden prepares to leave the political stage in 47 days, many of his former colleagues have been quick to criticize his decision to pardon his son, or, as in Mr. Schumer’s case, they have allowed all that they are not saying to defend Mr. Biden do the talking.