Will he or won't he... stand for the Tory leadership?
Speaking after his arrival back from a business trip to Vietnam, he said: "I've made a decision, but I've just come back from a trip and I'm going to be consulting further with my friends with whom I've been in contact by telephone from Vietnam for the last week".
But Mr Clarke rubbished the suggestion he had lost ground by going abroad as other contenders entered the race, saying anyone who had been put off by a three day wait could not have been a very strong supporter.
He added: "I do think the decisions the Conservative Party has got to make are serious, long term and are going to affect the next four to eight years."
Asked if he would be the fifth leadership contender, he replied: "The way we are going there will be an enormous amount of candidates."
Michael Ancram, who quit his post as Tory chairman on Thursday, entered the leadership race the same day hot on the heels of right-wingers Iain Duncan Smith and David Davis.
On Friday, Mr Ancram refused to express an opinion about whether Mr Clarke should run, choosing instead to set out his stall for the job.
He said that in the wake of the Tories' second landslide defeat the party should stand back and have a period of reflection and renewal.
Mr Clarke now faces pressure to declare his candidature from the pro-euro wing of the party.
If he does run he will be the only pro-single currency candidate in the ring.
Portillo the favourite
Mr Portillo has already stolen a march on the other candidates and is the hot favourite with the bookmakers.
He has also won widespread support from the shadow cabinet, including on Friday the backing of shadow health secretary Dr Liam Fox.
Mr Ancram is being viewed by many as a "stop Portillo" candidate in the absence of Mr Clarke, but he has denied that he is putting himself forward as a "caretaker leader" saying that he was "fighting to win".
Asked on BBC Radio 4's Today programme whether he could envisage giving Mr Portillo a place in a shadow cabinet led by him, Mr Ancram said he had not given the matter a moment's thought.
He said it was time to put an end to the Tories' "bitterness and rancour" and called for "radical policies" that were both electorally appealing and consistent with the party's principles.
Although he did not mention the shadow chancellor by name, he made a clear side-swipe at Mr Portillo when he said the party must not "follow the winds of fashion and fads".
Mr Portillo and Mr Duncan Smith began setting out their manifestos for the top Tory job on Thursday, both placing an emphasis on the need to embrace wholehearted change.
Tory ballot
Mr Ancram, Mr Portillo, Mr Davis, Mr Duncan Smith and possibly Mr Clarke will enter a ballot of Conservative MPs before the final two are chosen by all 350,000 Conservative party members.
Other possible candidates still considering their options include John Redwood, who has made two previous challenges in the past - including one against incumbent prime minister John Major in 1995.
Bookmakers William Hill have slashed the odds on Mr Ancram taking over from William Hague from 50/1 to 9/1 on news of his official entry.