Four Coloradans are among 44 former U.S. senators who published a letter Tuesday in the Washington Post urging “current and future senators to be steadfast and zealous guardians of our democracy.” Signing on to the bipartisan letter from Colorado were Republican Ben Nighthorse Campbell and Democrats Gary Hart, Mark Udall and Tim Wirth. Related Articles Trump says military to build border wall if Democrats refuse In possible plea deal, accused Russian agent case ‘resolved’ Russians interacted with at least 14 Trump associates during campaign, transition Russia investigation initially looked at 4 Americans, Comey says Republican anxiety spikes as Trump faces growing legal and political perils The letter says “we are entering a dangerous period” as Robert Mueller’s investigation nears its conclusion and the House prepares to investigate President Donald Trump and his administration. “At other critical moments in our history, when constitutional crises have threatened our foundations, it has been the Senate that has stood in defense of our democracy,” the letter says.