Biden, Warren battling for top spot heading into Tuesday's 2020 Dem debate

A new national poll on the eve of the Democrats’ fourth-round presidential primary debate showed Sen. Elizabeth Warren of Massachusetts and former Vice President Joe Biden locked in a close race for their party’s nomination.

Warren stood at 30 percent support in a Quinnipiac University survey Monday of Democratic voters and independents who leaned toward the party. Biden, the unrivaled front-runner until Warren’s surge in the polls the past couple of months, was at 27 percent.