By Katharine Jackson WASHINGTON (Reuters) – Republican U.S. Representative Liz Cheney warned that the nation’s democratic system is threatened by ongoing efforts to deny the legitimacy of Donald Trump’s 2020 election loss. “People must pay attention. People must watch, and they must understand how easily our democratic system can unravel if we don’t defend it,” Cheney said during an interview broadcast on CBS Sunday Morning, days before Congress’ official probe of the Jan. 6, 2021, assault on the Capitol begins public hearings. Cheney, a vocal critic of Trump who voted to impeach him, is one o…