WASHINGTON (Reuters) -U.S. Senate Republican hopeful Mo Brooks pledged on Monday to “fire” Senate Republican leader Mitch McConnell, days after former President Donald Trump told an interviewer that he could pull his endorsement of the Alabama congressman. “Today, I unveil my pledge to America, to fire Mitch McConnell. If elected to the Senate, I will not vote for Mitch McConnell for leader,” Brooks said in a 90-second digital ad. “America can’t afford a Senate leader who is a weak-kneed, debt-junkie, open-border RINO Republican, and who – worse yet – sells out America for special interest gro…