Donald Trump is expected to endorse House Speaker Paul Ryan R-Wis., Friday, two highly placed Republican sources tell Fox News -- just days after the Republican presidential nominee declined to back Ryan when asked in an interview. ADVERTISEMENT Ryan will face primary challenger Paul Nehlen in next Tuesday’s primary election for his congressional seat. Trump is expected to endorse the 2012 Republican vice presidential nominee at an event in Green Bay. While Ryan picked up the endorsement of Trump’s running mate, Indiana Gov. Mike Pence, Trump declined to endorse Ryan when asked in an interview Tuesday with The Washington Post....