Soros, who became nationally prominent in 2004 when he spent more than $20 million on independent groups supporting Sen. John Kerry (D-Mass.), will give $1 million to Priorities USA Action — which is supporting Obama — and $500,000 to Majority PAC and House Majority PAC, which are running ads on behalf of Democratic candidates for Congress.

The move could signal a softening of resistance by Soros and other wealthy liberals to contributing to super PACs and other independent groups that can accept unlimited donations. Soros had previously given $1 million to the American Bridge opposition research group and smaller checks to other groups, but had suggested he was unlikely to get involved more directly.