A fed-up CNN anchor Anderson Cooper cut off a former Republican congressman three times as the ex-lawmaker tried to defend Donald Trump’s assertion Sunday that one-fifth of mail-in ballots in a key battleground state are “fraudulent.” The former Republican president took to Truth Social on Sunday afternoon to promote the baseless claim that “20% of the Mail-In Ballots in Pennsylvania are fraudulent.” “Here we go again! Where is the U.S. Attorney General and FBI to INVESTIGATE? Where is the Pennsylvania Republican Party?” wrote Trump. “We Will WIN Pennsylvania by a lot, unless the Dems are allo…