California Gov. Gavin Newsom is keeping his distance from the campaign against Proposition 40, a proposed one-time 5% tax on the assets of the state’s wealthiest residents, despite previously emerging as one of its most prominent opponents, Politico reported Friday.

Newsom lobbied supporters to withdraw the measure, arguing it could drive wealthy residents and businesses out of California. But he is not fundraising or leading opposition messaging as the measure creates a political test ahead of a 2028 presidential bid.

The proposal has split Democrats, with the California Labor Federation and California Democratic Party backing it, while Newsom, Republican gubernatorial nominee Steve Hilton, Democrat Xavier Becerra, and unions oppose it.

Politico reported that Newsom aides remain in contact with the opposition campaign. Polling has shown the tax with, at best, a narrow lead, while billionaires including Google co-founder Sergey Brin are spending tens of millions of dollars to defeat it.

Read more at Politico.