Sam Gyimah has pulled out of the Tory leadership before the race has even begun.
The pro-Remainer is the only one who was calling for a second referendum.
Mr Gyimah, who is a prominent supporter of the People's Vote campaign, said he entered the contest to "broaden the debate and bring the diverse views of millions on Brexit to the fore."
He said: "It has been a tremendous privilege to be able to make the case for a new referendum as a credible solution to break the Brexit deadlock.
"I am hugely appreciative of the support I have received, both in public and in private.
"But I have reached the conclusion that, having entered the race at such a late stage, there simply has not been enough time to build sufficient support, and I have decided to step back.
"My purpose in campaigning for a solution to the Brexit deadlock, and bringing new ideas to help my party win over modern Britain, will not change.
"I wish all the contenders the very best at this challenging time as they make the case to take our country forward."
It has left the list with 10 candidates vying to be the next Tory leader.
Responding to the decision of pro-final say candidate Sam Gyimah to withdraw from the Tory leadership contest, Best for Britain COO Naomi Smith said: "It's sad to see the one reasonable candidate in this vile Tory leadership race have to drop out.
"With only Brexit advocates left in the race, it's more important than ever that remain parties work together.
"Our petition, calling for those politicians to work together in the national interest, just smashed through 50,000 signatures - showing strength of feeling across the country for politicians to put their differences aside to resolve this crisis."
