Regular Fox News guest Sean Parnell on Wednesday announced that he will challenge Democratic Rep. Conor Lamb in Pennsylvania's 17th Congressional District. President Trump praised Parnell earlier this month during a visit to Pittsburgh, saying he would be a formidable challenger to Lamb. "I am so excited to announce that today I'm declaring my candidacy for the great people of Pennsylvania's 17th District for Congress of the United States," Parnell, an Army veteran, said in an appearance on "Fox & Friends." *** Lamb, a Marine veteran and rising star in the Democratic Party, defeated former Rep. Keith Rothfus (R-Pa.) in...