What would fear of Sanders in the White House mean for the economy, even before the election? If he enters office with a Democratic Congress, he could accelerate the national transition from a relatively free market to a planned economy, with direct and indirect state control of the means of production. His Marxist views have altered little in the last five decades.
Both Main Street and Wall Street would price in these potentials, and if Sanders runs away with the Democratic nomination and leads in general election polls against Trump, the economic results would be frightening. Money would flee to greener pastures in offshore accounts, commodities, or even under mattresses. Growth is the well from which both economic opportunity for the middle class and tax dollars spring. The specter of a socialist victory would seriously damage the current economic boom.
For all the talk of billionaires being harmed by socialist policy, the rich have financial flexibility to take their assets out of danger. Middle class workers, however, would be much more exposed to the repercussions of capital flight.