The fast-moving coronavirus was something of an afterthought in that debate. Now the escalating crisis is likely to dominate it. Rising infections in the United States and around the world have prompted a dramatic slowdown of global travel, upended financial markets, and raised questions about President Donald Trump's ability to lead the nation through a prolonged period of uncertainty.

Just two Democrats — former Vice President Joe Biden and Vermont Sen. Bernie Sanders — remain to make the case that they are best-positioned to challenge Trump in November. Five other candidates who joined them on stage in the Feb. 25 debate in South Carolina have dropped out, with many rallying behind Biden's surging candidacy.

For both Biden and Sanders, the debate is a moment to display their leadership skills in front of what could be one of the largest audiences of the primary. They'll aim to draw a contrast with Trump, but also with each other, arguing that they have the right experience, temperament and policy prescriptions to lead the nation through a crisis.