New York (CNN Business) A day after a surprise interest rate cut failed to calm investors, a new surprise entered the calculus: former Vice President Joe Biden's strong showing in Super Tuesday voting.

Just two weeks ago, the market hit all-time highs as Senator Bernie Sanders became the front-runner. This morning, it is bouncing because Biden has taken the lead.

"Stock investors sent up a roar and piled back in overnight because a moderate Democrat had moved back into contention in the race for the White House," says Chris Rupkey, chief financial economist at MUFG Union Bank.

What's changed? The market view is that the coronavirus has hobbled President Donald Trump. Wall Street still wants Trump to win, but if a Democrat is going to be the next president, Wall Street could live with Biden.

Sanders has taken a much harder line on regulating Wall Street, taxing the rich, rolling back corporate tax cuts and remaking the economy with expensive health care and education plans. Biden -- longtime senator from a state that is home to credit card companies -- is seen as more moderate, a steady hand ready to work across the aisle.

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