Four leading Democratic advocacy groups said Friday that they raised $25 million in the second quarter, marking a notable improvement over their dismal numbers earlier in the year.

The super PACs and affiliated groups — Priorities USA Action, Majority PAC, House Majority PAC and American Bridge 21st Century — are combining forces to run ads and share opposition research in both the presidential race and congressional contests, although each has its own specialty. Priorities USA, for example, is a super PAC run by former aides to President Obama that has been running ads attacking Mitt Romney for his career as a private equity manager.

Although the numbers have grown from earlier in the year, liberal groups are still likely to be dramatically outspent by their opponents on the right. For example, Crossroads GPS, a group founded with the help of GOP political guru Karl Rove, is spending $25 million on a swing-state ad campaign just for the month of July.

“Karl Rove, the Koch Brothers, and their right wing allies are preparing to spend overwhelming amounts of money to flood Washington with supporters of their extreme agenda,” the groups said in a joint statement. “Together we’re ensuring that Democrats will have the resources to level the playing field and fight back against the right’s attacks in order to keep the White House, maintain a majority in the Senate and take back the House.”

Priorities USA, whose prominent donors include Hollywood mogul Jeffrey Katzenberg and cable television host Bill Maher, said it raised $11.7 million from April to June. Majority PAC, which focuses on Senate races, raised $5.4 million; House Majority PAC, focused on House districts, took in $4.3 million; and American Bridge, which focuses on opposition research, raised $4.1 million through its super PAC and nonprofit.

Among the new donors is liberal financier George Soros, who gave $1 million to the American Bridge super PAC.

The four liberal super PACs and affiliated groups collectively raised $10.4 million in the first quarter.

Obama and other Democrats have sounded the alarm in recent weeks about a potential fundraising gap with Romney and conservative groups. The new numbers for the four liberal groups have grown since January, when Priorities USA reported raising a paltry $59,000.