U.S. President Joe Biden warned that a Republican win in Tuesday's midterm elections could weaken U.S. democracy, while former President Donald Trump hinted at another White House bid, two days before votes in which Republicans could gain control of both chambers of Congress.

The comments, made at dueling rallies held in New York and Florida, highlighted the grim prospects that Biden's Democrats face, despite fulfilling his promises to boost clean-energy incentives and rebuild crumbling roads and bridges.

Republicans have hammered Biden for high inflation and increased crime in the wake of the COVID-19 pandemic, and nonpartisan forecasters favor them to win control of the House of Representatives — and possibly the Senate as well. Democrats' early leads in Senate races in Georgia, Pennsylvania and Nevada have evaporated.