Rick Santorum has lost the first battle in the fight to be the Republican candidate for the White House, the Iowa caucuses, to Mitt Romney by just eight votes.

Mr Santorum has been an outspoken critic of President Barack Obama's healthcare programme and has said that similar policies brought about the collapse of the British Empire.

Here Newsnight's Peter Marshall challenges Mr Santorum on what he meant by that statement.

Broadcast on Tuesday 3 January 2012.