Rick Santorum has pulled out of the race to become the Republican party candidate for US president. Mr Santorum is an outspoken critic of LGBT rights and had pledged to invalidate the marriages of gay couples if he won the presidential election.

Mr Santorum told a press conference: “We made a decision over the weekend, that while this presidential race for us is over, for me, and we will suspend our campaign today, we are not done fighting.”

The former Pennsylvania senator was keen to stress that his bid went further than anyone else had expected, describing his campaign “as improbable as any race that you will ever see for president.”

“Against all odds,” he said, “we won 11 states, millions of voters, millions of votes.” He had won the apparent backing of media mogul Rupert Murdoch who had tweeted that Mr Santorum was the “only candidate with genuine big vision for country.”

By bowing out, Mr Santorum effectively clears the path for Mitt Romney to become the official Republican candidate. Mr Romney’s position on gay rights was recently described by the actor George Clooney as being on “the wrong side of history.” Clooney went on to say, “everyone sort of understands [gay rights] might be the last leg of the civil rights movement, I do believe that.”

In January, Mr Santorum told NBC that he would support a federal amendment to the constitution which had the effect of dissolving existing unions.

Answering a question on whether gay couples would be forced to divorce under the amendment, he said “Well, their marriage would be invalid. If the constitution says ‘Marriage is this’, then people whose marriages are not consistent with the constitution…”

A few days later, Mr Santorum was booed in New Hampshire during a heated debate in which an audience member asked how marriage equality would harm him.

He said: “Marriage is the union of a man and a woman. God made men and women. Men and women come together in a union to have children. It should be valued and have privileged status over people who want to have a relationship together.

“The uniqueness of marriage is it provides an intrinsic good to society. It’s the union that causes children to be born and raised in an environment that’s a birthright.

“When we deny children that birthright by saying other types of relationships are okay, I think we are harming children.”

Later in January, Mr Santorum was asked what he’d do if he had a gay son. He said: “I would love him as much as I did the second before he said it, and I would do everything I can to be as good a father to him as possible.” Santorum has in the past talked of a “hate the sin, love the sinner” policy towards homosexuality.

In February, The Unicorn Booty blog published a collage by an unidentified artist who has taken hundreds of stills from pornographic films and blended them to form a portrait of Mr Santorum.

Last month, Mr Santorum and Dan Savage, the creator of the It Gets Better campaign to combat LGBT teenage suicide had a very public row.

Mr Santorum told Clear Religion: “I would tell him [Savage] that I’m praying for him. He obviously has some serious issues. You look at someone like that who can say and do the things that he’s doing and you just pray for him and hopefully he can find peace.”

Savage launched a tongue in cheek campaign back in 2003 to redefine ‘Santorum’ on Google as “the frothy mix of lube and fecal matter that is sometimes the byproduct of anal sex.”

Responding to Mr Santorum’s offer to pray for the columnist and campaigner, Mr Savage told a blogger: “Rick Santorum thinks that women who have been raped should be compelled—by force of law—to carry the babies of their rapists to term, he thinks birth control should be illegal, he wants to prosecute pornographers, etc., etc., basically the guy wants to be president so that he can micromanage the sex lives of all Americans…and I’m the one with issues? Because I made a dirty joke at his expense eight or nine years ago and it stuck? I’m the one with issues? Rick can pray for me. I’ll gay for him. And we can call it even.”