PHILADELPHIA — Sean Parnell, a decorated combat veteran and favorite of former President Donald Trump, is all but certain to run for U.S. Senate in Pennsylvania, according to a Republican official who spoke with Parnell this week. "He said he was 99% sure this is what he was going to do," said Sam DeMarco, the Republican chairman in Allegheny County, where Parnell came up just short in a high-profile bid for Congress last year. "If he does make that decision, he's going to be a formidable candidate." Parnell has begun calling top GOP officials in Pennsylvania to discuss a potential 2022 Senate...