The top outside-money group supporting President Obama raised $10 million in August, logging its best fundraising month yet.

The super PAC known as Priorities USA Action confirmed the total to ABC this morning. The group topped its next-highest total, of any month this year, by nearly $4 million. The group's next-best haul was $6.16 million in June.

In money raised, Priorities has lagged behind its pro-Romney counterpart, Restore Our Future, which reported taking in $20.7 million in June and $7.5 million in July. Along with the Karl-Rove-co-founded super PAC American Crossroads and 501(c)4 nonprofit Crossroads GPS, Republican groups have threatened to overwhelm the Democratic outside-money operation.

A Priorities spokeswoman would not disclose fundraising figures for the sister 501(c)4 group, Priorities USA, which is far more secretive, disclosing no donors or fundraising totals except to the Internal Revenue Service. Much of the big, outside money in this election year may well remain undisclosed in a handful of 501(c)4 groups, including Priorities USA, Rove's Crossroads GPS and the Koch-backed Americans for Prosperity.