U.S. stocks slumped on Tuesday under the weight of another jump for the price of oil. It was a return to form for financial markets after Wall Street’s worries about Israel’s fighting with Iran had seemed to calm a bit on Monday.

Degrading Iran's nuclear and military capabilities is good for geopolitical stability, which would be good for markets, Eisman said.

Stocks rose and oil prices retreated on Monday as investors shrugged off the continuation of hostilities between Israel and Iran over the weekend.

Financial markets may be in for a "knee-jerk" selloff if the U.S. military attacks Iran, with economists warning that a dramatic rise in oil prices could damage a global economy already strained by President Donald Trump's tariffs.