First, Prime Minister David Cameron effectively ran away from the mess he created, and then Boris Johnson, who everyone assumed would step in to fill his place, didn't.
The result is expected to be announced on September 9.
The victor will become the second woman prime minister in Britain after Margaret Thatcher.
"She is now well placed to win and replace the absurd gloom in some quarters with a positive, confident and optimistic approach, not just to Europe, but to government all round", he said.
'This vote shows that the Conservative Party can come together - and under my leadership it will.
However, several senior party members have urged for the contest to be announced earlier due to the fallout of Britain's BREXIT vote and the need to begin European Union exit negotiations.
"Following last week's referendum, our country needs strong leadership to steer us through this period of economic and political uncertainty", May said in launching her bid last week.
The leader of the Scottish Conservatives has said she will be backing Theresa May as the next Tory leader and United Kingdom prime minister.
Now there are only two, with the 150,000 members of the Conservative Party set to choose between the remaining candidates, who will campaign for their votes over the summer.
Amber Rudd, one of Mrs May's backers, has dismissed Mrs Leadsom's support in the Parliamentary party as "not in the same league" as those who backed Home Secretary.
He said May had the "track record" in matters of security as Home Secretary to take the country forward. Justice Secretary Michael Gove dropped out of the race after receiving only 46 votes, leaving May and Leadsom in a head-to-head battle for the post that David Cameron is vacating. Energy Minister, Andrea Leadsom finished with a total of 84 votes.
Mrs May and Mrs Leadsom will spend weeks trying to win over the party's largely eurosceptic membership, who may think a fresh face would stand a better chance in an election in 2020. Mrs May was campaigned to remain in the European Union, whereas Mrs Leadsom campaigned to leave.
Leadsom has only been an MP since 2010 and if elected she will be the least experienced prime minister since William Pitt the Younger in 1804.