Pennsylvania Senator Arlen Specter is the sixth senator to publicly flip on the issue of gay marriage this year. Specter, who recently returned to the Democratic Party after 44 Republican years, is the senior senator from Pennsylvania.

“The time has come to repeal the 1996 Defense of Marriage Act (DOMA),” Specter said in a Huffington Post editorial published Tuesday. “Enacted 13 years ago when the idea of same sex marriage was struggling for acceptance, the Act is a relic of a more tradition-bound time and culture.”

“Connecticut, Iowa, and Massachusetts have already passed laws recognizing same sex marriage and other states are moving in that direction. The states are the proper forum to address this divisive social and moral issue, not the Federal Government with a law that attempts to set one national standard for marriage.”

Specter voted in favor of DOMA; ten years later he supported a constitutional amendment to ban gay marriage. Specter told The New York Times that he does “not recall ever being in favor of a constitutional amendment to ban state action.” Specter voted in favor of the idea in the Judiciary Committee, the paper reminded readers.

In July, Vermont Senator Patrick Leahy backed down from his opposition to gay marriage. A month earlier, Connecticut Senator Christopher Dodd, a Democrat, endorsed gay marriage in a Senate blog post. “I am also proud to now count myself among the many elected officials, advocates, and ordinary citizens who support full marriage equality for same-sex couples,” Dodd said.

In January, Kirsten E. Gillibrand, the upstate New York congresswoman chosen by Governor David Paterson to fill the Senate seat vacated by Secretary of State Hillary Clinton, said “I will advocate for marriage equality” in her acceptance speech to the post.

New York Senator Charles Schumer told the New York Daily News in March that “equality is something that has always been a hallmark of America,” when asked to verify a press release by Empire State Pride Agenda, a group that lobbies for gay marriage in New York, that claimed the senator had reversed course on gay marriage.

And two months later, after the Iowa Supreme Court legalized gay marriage, Iowa Senator Tom Harkin also made an about-face. Speaking on the PBS program Iowa Press, Harkin said he would vote against a ban on gay marriage in Iowa.

“You know there's always going to be some who feel that they have to push this issue [gay marriage], and, for whatever reason, they are going to push it and try to divide people, but they're on the losing end. They are on the losing end of history,” Harkin said.

Specter's announcement was quickly criticized as a political maneuver by his 2010 Democratic nomination rival, Representative Joe Sestak, a long-time gay marriage supporter.

In a statement released Tuesday, Sestak accused Specter of running away from “his 30-year Republican record.”

“Senator Specter's willingness to reposition himself just to help himself politically should give pause to Pennsylvanians who are looking for a loyal senator who will put principle over politics for the next generation,” Sestak said.

But while the five senators that flipped before Specter hail from states where gay marriage is legal or, in the case of New York, there is widespread support for it, polls indicate a majority of voters in Pennsylvania do not support gay marriage.