The defeat of former front runner, Mr Michael Portillo, now leaves the 300,000 members of the British Conservative party with a clear choice between right and left. Indeed the absence of clarity as to where he stood on issues dear to Tory hearts may have played a significant part in Mr Portillo's defeat.
His move from the right towards the centre and his switch from sharply identifiable views to a softer focus, marked him out as someone rank-and-file Tories found difficult to trust. His admission of a homosexual relationship when young and his views on cannabis raised the spectre that he might be a closet liberal.
Mr Iain Duncan Smith suffered from none of these disadvantages. An intensely Eurosceptic politician, his true-blue credentials are enhanced by his committed support of the death penalty - in the form of hanging for humans and "country sports" for less desirable animals.
Mr Clarke comes from a very different background. No-one within the Conservative party is more pro-European. No-one epitomises the "one-nation" wing of the party as strongly as he does. However Britain's "one-nationists" have a champion with considerably greater vote-getting ability and more substantial public visibility. His name is Tony Blair.
To a very large extent, Mr Blair is the man to beat in the Tory leadership race. It is here that Mr Clarke may have an advantage. Polls have consistently shown him to be the candidate whom party activists believe would be most likely to lead them to victory in the next election.
In the scale of political values, winning elections always comes well ahead of ideological considerations. The Conservatives may be deeply divided on Europe and the pound sterling, but there is no dissent when it comes to the idea of taking power once more.
In the immediate aftermath of yesterday's vote, Mr Clarke would appear to be the favourite, but the race is not over yet.
One of the severe blows to Mr Portillo in the latter days of the campaign, was a statement from Baroness Thatcher in which she effectively disowned him.
It would be naive to think that the former Prime Minister will remain neutral for the rest of the campaign and Mr Duncan Smith is her type of politician with her type of views. While her endorsement could ensure success in the leadership race, it might have the opposite effect on the next general election.