Mueller: Russian interference serious challenge to democracy

WASHINGTON -- Former Trump-Russia special counsel Robert Mueller told lawmakers at the start of back-to-back hearings Wednesday that the Russian government's efforts to interfere in the U.S. presidential election are among the most serious challenges to American democracy he has seen.WATCH LIVE NOW: Robert Mueller testifies before U.S. CongressThe televised Capitol Hill appearances, Mueller's first since wrapping his two-year Russia probe last spring, are unfolding at a moment of deep divisions