Mitt Romney is now the only Republican officially running for president in the District of Columbia.

Josh Romney, the third-oldest son of the former Massachusetts governor, handed in a stack of 700 signatures at the D.C. Board of Elections on Wednesday, accompanied by two local campaign supporters in Republican National Committeewoman Betsy Werronen and D.C. State Board of Education member Patrick Mara. As of yet, no other candidate has completed D.C.'s filing process, though three have started it.

"Sorry for this - we appreciate it," Josh Romney told the registrar on duty, smiling as a few cameras flashed with reporters looking on. "I guess you have to do this a few more times."

"Probably," she replied.

The heavily Democratic district isn't generally a hotbed of Republican primary competition. After its April 3 presidential primary, D.C. will send just 19 voting delegates to the Republican National Convention in Tampa, Fla., out of over 2,200 delegates total - fewer than every state except New Hampshire (12), Vermont (17), Delaware (17) and Rhode Island (19).

Republicans could face a drawn-out primary process in 2012, after the Republican National Committee changed its rules and pressured states to reject winner-take-all rules for delegate allotment, and it's narrowly conceivable that every delegate vote could count.

The Romney campaign had already paid a $5,000 filing fee to the D.C. Republican Party, as have Rep. Ron Paul, R-Texas, former Utah Gov. Jon Huntsman, and former House Speaker Newt Gingrich, R-Ga., all of whom have taken initial steps to file for candidacy in D.C.