I'm sorry, I thought we were talking about the Republicans, LOL.
Samuel Chase, a SC justice, was impeached in 1805, but not convicted by the senate.The stated reason was certain legal improprieties in a libel case. The real motivation was political; Jefferson was upset that the Federalists were starting to create the concept of judicial review. I don’t know whether Kagan’s failure to recuse could constitute an impeachable offense, but maybe she doesn’t want to take that chance.