President Donald Trump's arsenal for overturning the election will soon be down to one final, desperate maneuver: pressing his Republican allies on Capitol Hill to step in and derail Joe Biden’s presidency. Although the Electoral College casts the official vote for president on Dec. 14, it’s up to Congress to certify the results a few weeks later. And federal law gives individual members of the House and Senate the power to challenge the results from the floor — a rarely used mechanism meant to be the last of all last resorts to safeguard an election... Here’s how Trump’s defenders in...