President Trump made his second campaign trip on behalf of Montana GOP Senate candidate Matt Rosendale on Thursday, aiming to lift his chances against incumbent Democratic Sen. Jon Tester, who Trump accuses of defaming his personal physician, scuttling his nomination to lead the Department of Veterans Affairs.

Trump fixated on Tester’s role in Dr. Ronny Jackson’s unsuccessful nomination, telling a crowd in Billings, Mont., that “one of the saddest things I have seen” is what Tester “did to a great, great man, Adm. Ronny Jackson. Adm. Jackson was subjected to horrible lies and smears.”