Top Democrats join the wealthiest in fighting a California tax increase on billionaires

A first-in-the-nation proposal in California to tax billionaires could test voters' appetite for levying a wealth tax on the ultra-rich. Vermont Sen. Bernie Sanders is headlining events to urge Californians to pass the measure. But it faces significant political headwinds. Billionaires are spending millions to fight the tax. And Democratic Gov. Gavin…