Mayor Eric Adams’s federal indictment on corruption charges has left him with few political friends, but he has found a kindred spirit and a surprisingly steadfast ally in Donald J. Trump.

The former president has repeatedly defended Mr. Adams as Election Day draws closer, arguing that they are similarly being targeted by overzealous prosecutors.

His latest show of support came on Thursday night at the Alfred E. Smith Memorial Foundation Dinner, a Catholic charity event in Manhattan that has become a near-required stop for presidential hopefuls.

“I know what it’s like to be persecuted by the D.O.J. for speaking out against open borders,” Mr. Trump said, referring to the Justice Department. “We were persecuted, Eric. I was persecuted, and so are you, Eric.”

Politics and indictments make for strange bedfellows, and it was a remarkable show of solidarity between a former Republican president and the Democratic mayor of the nation’s largest city and a liberal stronghold.

If the mayor were to be convicted and the former president were to return to the White House, Mr. Trump’s embrace of Mr. Adams has raised the prospect of a presidential pardon. Mr. Trump could also pressure the Justice Department to seek a more lenient approach at sentencing, or commute Mr. Adams’s sentence as he did in 2020 for Rod R. Blagojevich, a former Democratic governor of Illinois who was convicted of corruption.