Joe Biden's standing in the
Democratic presidential nomination battle has slipped in Iowa against top rivals including
Elizabeth Warren, the frontrunner in the early-voting state, who on Friday answered critics over how she will pay for her progressive policies.
As candidates battle for supremacy in the crowded race to see who will challenge US President
Donald Trump in November 2020, Warren took the risky political gamble of unveiling a $20.5 trillion Medicare for All plan.
How to pay for expanding and improving health care has become a flashpoint of the Democratic race, with Warren and her fellow progressive Senator Bernie Sanders pushing a sweeping transition to universal health care and the centrist Biden seeking to build on the existing Obamacare system.