Joe Biden and Lindsey Graham were great friends. Then came impeachment.

While Democrats build the case that Trump tried to pressure Ukraine into damaging his political rivals — by investigating Biden and his son Hunter — Graham has joined Republicans to argue that the Bidens should, in fact, be probed.On Monday, Biden’s wife, Jill, suggested an across-the-aisle bond has suffered lasting damage.“I don’t know what happened to Lindsey,” Jill Biden said on CNN’s “New Day,” criticizing Republicans’ focus on her son amid impeachment proceedings against the president.“We used to be great friends,” she said of Graham. In November, Graham asked the State Department for documents related to Burisma and information on calls between the former vice president and Ukraine’s president at the time.Biden was dismayed.“Lindsey is about to go down in a way that I think he’s going to regret his whole life,” he said the same week on CNN, suggesting Graham was eyeing his reelection prospects as he stood staunchly with Trump. “Yes." Berman noted the use of past tense.Had the relationship changed?“It’s hard when you, I don’t know, consider somebody a friend and then they’ve said so many things — so many negative things,” Jill Biden said.Greg Jaffe and Matt Viser contributed to this report.Read more:Trump’s team dismisses the case for impeachment as weak — and then sloppily attacks Joe BidenLindsey O.