UK Independence Party (Ukip) leader Lord Pearson of Rannoch announced he was stepping down today - saying he was not good enough at the job.
The peer, who only took charge in November, said the party "deserved someone better" to put the case for leaving the European Union.
The move could open the way for a return by Nigel Farage, who quit as leader to concentrate on his failed attempt to oust Commons Speaker John Bercow from Parliament at the general election.
In a statement this morning, Lord Pearson said: "I took over as leader of Ukip last year to see the party through the General Election, and said I would then consider my position.
"We increased our vote by 50%, and have many exciting plans for the future.
"But I have learnt that I am not much good at party politics, which I do not enjoy.
"I am also 68, and need to give more time to my wider interests...
"So it is right that I should stand down on September 2, early in the Parliament, to give a younger leader time to be established before the next election, which may come sooner than we think.
"There is no shortage of talent in Ukip, and the new leader will have my full support."
He added: "Ukip deserves a better politician than me to lead it and show the country how liberating and enriching life would be outside the EU. I am confident that one will emerge."
Mr Farage, who suffered serious injuries in a plane crash on polling day, said he would consider standing for the leadership again if he was physically fit.
He sustained broken ribs, bruised lungs and facial injuries in the accident when the plane he was travelling in, towing a Ukip banner, nose-dived to the ground at an airfield in Northamptonshire.
He told BBC Radio 4's Today programme: "I think I've got to decide whether I'm physically up to it and if I am, well I may well throw my hat in the ring."
But he said he was not yet fully recovered from his accident on May 6 and his back was "not all that it should be" and would require at least one operation before Christmas.
"Whilst I feel very well within myself, I'm conscious that I just haven't, at the moment, got the kind of work capacity that perhaps is needed."
Mr Farage said Lord Pearson had acknowledged the difficulties he had faced as leader of the party.
"He was somebody who had been very successful in business, he was used to being in charge, looking at the facts, making decisions and then it happens.
"But of course in party politics it isn't like that because you have to carry your own party with you.
"I think he found, in the general election campaign, that was deeply frustrating."
He added: "Running a party, he didn't like it, he wasn't enjoying it and he felt it was right to go."