“The inside maneuvering can only go so far without the outside mobilization,” Speaker Nancy Pelosi noted on Thursday before signing the bill, the last official act by Congress before transmitting it to the White House so it could become law.
The push was led by Ken Mehlman, President George W. Bush’s campaign manager in 2004 and a former chairman of the Republican National Committee who came out as gay in 2010, and Centerline Action, a centrist nonprofit funded by him and Reginald Brown, a lawyer in Mr. Bush’s White House, among others.
It involved flooding the phone lines of Republican senators with calls from constituents who favored the same-sex marriage measure, presenting them with polling that showed that voters were more likely to support a proponent of the bill than somebody who opposed it, and a public pressure campaign aimed at demonstrating widespread conservative support for the legislation.
“When this popped in the House, we immediately went into action and reached out to all of those operatives and supporters and activists who had been engaged in this issue and kind of got the gang back together,” said James Dozier, the president of Centerline’s board. A former Republican congressional aide, Mr. Dozier is married to a man and has long pressed for same-sex marriage rights.
The work got underway in July, after 47 Republicans — a surprisingly high number — joined Democrats in supporting the bill when it initially passed the House. While the G.O.P. backers amounted to less than a quarter of the party’s contingent in that chamber, the degree of bipartisanship was enough to transform the measure from a mere messaging exercise into a serious legislative effort.