WASHINGTON — An outside group founded this spring by two former Obama White House advisers has raked in millions in donations since April, relying in part on top-flight fundraisers and labor unions to counter GOP-leaning ads critical of the president and congressional Democrats.

Priorities USA Action, an independent group founded by former Obama aides Bill Burton and Sean Sweeney, said Sunday its donations included $2 million from film producer Jeffrey Katzenberg, as well as $500,000 each from Fred Eychaner, founder of Chicago-based Newsweb Corp., and the Service Employees International Union.

Priorities USA Action and sister organization Priorities USA have raised more than $5 million since this spring, Burton said Sunday. Those amounts paled in comparison to the $86 million raked in by the Democratic National Committee from April through June, as top donors focused on President Barack Obama's first fundraising quarter.

Burton said Priorities has had a major impact with targeted local advertisements — tallying more than $700,000 — in part by making Medicare cuts a litmus test for Republican presidential candidates. That included a targeted ad against former Massachusetts Gov. Mitt Romney on Medicare.