His endorsement came as labor leaders voiced strong opposition to the measure. They argued that despite being presented as a tax on billionaires, Proposition 40 contains provisions that could potentially allow for the taxation of savings, retirement accounts, and home equity for all Californians. This, they contend, would disproportionately affect working families.

Labor representatives expressed concerns that the tax could impact the retirement security and homeownership of individuals who have worked for decades to build their assets. They emphasized that these are not unearned fortunes but the result of hard work and 'sweat equity.'

Proposition 40 was reportedly initiated by a healthcare union to address potential federal healthcare funding cuts. However, its potential economic ramifications and the possibility of broader taxation have become central points of contention, drawing significant campaign spending, with most contributions opposing the measure.