US election 2016: Republican Rick Santorum drops White House bid and endorses Marco Rubio

Rick Santorum has become the third Republican candidate to suspend his campaign in as many days. Following a disastrous Iowa caucus – which he won in 2012 – Santorum made the announcement on Fox News hours after Rand Paul dropped his bid and two days after Mike Huckabee suspended his campaign.

During his interview, the conservative former Pennsylvania senator also endorsed Grand Old Party (GOP) rival Marco Rubio. "I don't endorse lightly," Santorum said, calling Rubio a "natural born leader".

The former Iowa Caucus winner found himself overshadowed by a number of candidates in the Republican field in this year's caucus. After finishing in 11th place with less than one percent of the vote in Iowa, Santorum told The Des Moines Register that he would be reassessing his bid.

"We are going to spend a couple of days just thinking and praying, and figure out what we are going to do, and we will make a decision," he said. By 2 February he had postponed a campaign tour of South Carolina that was set to start on 3 February. South Carolina will have its Republican primary election on 20 February.

February has kicked off a key period of the 2016 presidential election. Following the 1 February Iowa Caucus, Democratic presidential candidate Martin O'Malley ended his long-shot bid to the White House. O'Malley was followed quickly by Republican hopefuls Huckabee, Paul and Santorum. The remaining candidates have now focused their attention on New Hampshire ahead of the 9 February primary election.