Priorities USA Foundation is the 501(c)(3) arm of the left-of-center advocacy group Priorities of USA Action, which is affiliated with Priorities USA, a major Super PAC that supports Democratic Party candidates.
Priorities USA Foundation is a 501(c)(3) nonprofit.
In its first year of operation (2017), the group gave $50,000 to the New Venture Fund, a major left-wing funder managed by the consulting firm Arabella Advisors, with a grant description indicating the money was to be gifted to America Votes, a left-wing 501(c)(4) voter engagement group.  New Venture Fund gave more than $700,000 to America Votes in 2017, according to its 2017 tax returns. 
Priorities USA Foundation received IRS tax exemption in February 2017. Its IRS determination letter is available here.
Priorities USA Foundation’s IRS Form 990 filing for 2017 is available here.