LOS ANGELES — George Papadopoulos, a former Trump campaign aide who was a key figure in the FBI’s Russia probe, filed paperwork Tuesday to run for the U.S. House seat being vacated by Democrat Katie Hill. Papadopoulos didn’t immediately comment, but on Sunday he tweeted, “I love my state too much to see it run down by candidates like Hill. All talk, no action, and a bunch of sellouts.” Hill, whose district covers Los Angeles County, announced her resignation on Sunday amid an ethics probe into allegations she had an inappropriate relationship with a staff member. She’s admitted to a consensual relationship with a campaign staff member, but denied one with a congressional staff member, which would violate U.S. House rules. She’s called herself the victim of revenge porn by an abusive husband she is divorcing. Papadopoulos, meanwhile, was a key figure in the FBI’s Russia probe into ties between Russia and the Trump campaign. That investigation began after revelations that P...