Proposition 40, which would impose a one-time 5% tax on California billionaires to help fund healthcare, appeared headed for defeat, though votes were still being counted.

Opponents raised hundreds of millions of dollars to fight the measure, far outspending supporters, who argued the tax could help offset federal healthcare cuts.

The campaign also faced opposition from Gov. Gavin Newsom, teachers, business groups and others, while voters weighed concerns about taxing assets and the possibility that billionaires could leave California.