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Tonight at 6 p.m., Mayor Adrian M. Fenty is celebrating his 37th birthday at the Walter E. Washington Convention Center, and you’re invited.

Well, actually, you’re weren’t exactly invited (as in, sent an invitation) unless you were one of the approximately 10,000 folks who attended Fenty’s inauguration ball back in January, but the public is welcome all the same.

The event is being paid for by the “D.C. Fund.” Now students of District political-finance history might recall that being the name given to Ward 2 Councilmember Jack Evanserstwhile political action committee (né “Jack PAC”), which he shuttered after taking criticism over its payments for travel and sports tickets.

That D.C. Fund, mind you, is dead; this D.C. Fund isn’t a political action committee, but rather a 501(c)(4) nonprofit organization. That means a couple of things: (1) Unlike a PAC, 501(c)(4)’s don’t have to report itemized contributions and expenditures, and (2) the group must be “operated exclusively for the promotion of social welfare” and its funds must be “devoted exclusively to charitable, educational, or recreational purposes.” Hence, a open-to-the-public birthday party with largely secret donors.

Here’s to recreational purposes!

Fenty spokesperson Carrie Brooks reports that the D.C. Fund contains the leftovers from the mayor’s inaugural festivities. The inaugural committee raised about $700,000, she reports, and about $500,000 of that was spent on the ball. The remainder is going toward the birthday party. A group of phone-bankers called the list of inaugural donors over the weekend asking for volunteers for tonight’s festivities.

Last December, the Fenty transition team released a list of donors to the inaugural, featuring such names as Bank of America, Chevy Chase Bank, and the Tenacity Group, accounting for about $200,000. As for the other half-million, there’s been no disclosure to date.

The party will feature live music and “light refreshments,” Brooks says, and there’s going to be room for 5,000.

So go get lightly refreshed tonight, and thank the D.C. Fund—-or rather, the Fenty Party Fund—-for the fun.