Republican presidential hopeful Rick Santorum has blamed the fall in numbers of married Americans on gay marriage.

The former senator referenced a report by the Pew Research Center which said the number of couples who married in the US was down 5% on the previous year.

Santorum tweeted: “Here is 1 effect of changing definition of marriage “@HuffingtonPost: Marriage rate in America drops to new low”

The Huffington Post pointed out today that the survey did not attribute its findings to marriage equality, but to the increase in other kinds of “socially acceptable” living arrangements.

Support for Santorum’s presidential bid is failing, as a poll this week by the same Pew Research Center saw 44% of Republican primary voters saying they would not consider backing him, compared with 3% who would definitely support his bid.

Newt Gingrich and Mitt Romney lead the poll, with 35% and 21% of voters respectively saying they support them in the nomination race.

Gingrich sufferd embarrassment this weekend when his half-sister, a lesbian rights campaigner, said he was “on the wrong side of history” when it came to gay rights.

Mitt Romney was also confronted by a gay war veteran in New Hampshire this week, who told him it was good to know he did not believe everyone was “entitled to their constitutional rights” on the question of gay marriages.

As Romney, who also ran for the 2008 nomination, left, the Vietnam soldier added: “You have to look a man in the eye to get a good answer and you know what, Governor? Good luck. You’re going to need it.”