Yesterday, on the way to an Intelligence Squared debate about campaign finance regulation, I happened to read a story about Roy McDonald, one of four Republican state senators who last year voted for the bill that legalized gay marriage in New York. McDonald did so only after receiving assurances from gay rights activists who promised to help counter the expected backlash by raising money for his re-election campaign. The New York Times reports that they delivered on that promise:

New York was the first state to legalize same-sex marriage with the support of a Republican-controlled legislative chamber, and gay-rights advocates, who have showered Mr. McDonald with campaign contributions, fear that his defeat would discourage Republican legislators in other statehouses from bucking their party to support same-sex marriage....

The race between Mr. McDonald and [Kathleen] Marchione [McDonald's opponent in today's primary] is the most expensive legislative primary in New York this year. Mr. McDonald has raised more than $926,000 in this campaign cycle, thanks in part to help from supporters of same-sex marriage, including Mayor Michael R. Bloomberg, who donated $10,300. Ms. Marchione, by contrast, has raised more than $180,000.

While McDonald says he voted his conscience, Marchione argues that he betrayed voters by changing his position on gay marriage, essentially selling his vote for campaign cash. The question I posed to the audience at last night's debate (which was held at the Kaufman Center in Manhattan): Is McDonald's vote an example of the corruption that campaign finance regulations are aimed at curtailing? The average progressive, I think, would say no: Supporters of gay marriage are simply expressing their gratitude to McDonald and showing that legislators can benefit politically by doing the right thing. But what McDonald did arguably amounted to a quid pro quo arrangement in which he agreed to support a particular bill in exchange for campaign contributions. In form it is no different from voting against a cigarette tax hike based on promises of donations from tobacco executives or voting against environmental regulations in anticipation of support from Archer Daniels Midland's political action committee. The only difference is that, from a progressive perspective, McDonald voted the right way.