Brexit figurehead Boris Johnson came top by a landslide in a first-round vote on Thursday for a leader to replace British prime minister Theresa May as the deadline for leaving the EU looms.
In the ballot of Conservative MPs, former London mayor Johnson secured more than twice the number of votes won by his nearest challengers as three of the 10 candidates were eliminated.
The outcome of the leadership battle could determine under what conditions Britain exits the European Union. It is scheduled to leave on 31 October.
Johnson secured 114 votes, way ahead of foreign secretary Jeremy Hunt, a distant second on 43, and third-placed Environment Secretary Michael Gove with 37.
"I am delighted to win the first ballot, but we have a long way to go," Johnson said as he thanked his supporters.
Thursday's secret ballot was Conservative MPs' first vote in the governing party's leadership contest. The eventual winner will become prime minister.
Johnson spearheaded the Leave campaign in the seismic 2016 referendum vote to quit the EU. He wants to secure a deal by the deadline but says as a last resort he would leave the bloc without a formal agreement between London and Brussels.
Opponents of "no-deal" say it would cause economic chaos as Britain breaks up with its top trading partners.
Hunt said he was pleased with his showing.
"We face a crucial choice: who can negotiate some better choices than the bad ones we face. The stakes have rarely been higher for our country. This serious moment calls for a serious leader," he said.
Former Brexit minister Dominic Raab (27), interior minister Sajid Javid (23), health minister Matt Hancock (20) and international development minister Rory Stewart (19) also secured the 17 votes needed to survive the cut.
Andrea Leadsom (11), Mark Harper (10) and Esther McVey (nine) fell below the threshold.
The seven remaining candidates go through to Tuesday's second round, when contenders will need the votes of 33 of the 313 Conservative MPs to stay in the contest.
May stepped down as party leader on Friday, having failed to deliver her plan for taking Britain out of the EU after nearly three years in the post.
She remains prime minister until a successor is chosen as head of the Conservatives.
May refused to say who she had backed in Thursday's vote, telling reporters: "That's none of your business!"
Fight for votes
The candidates reflect the divergence of views within the centre-right party on Brexit.
Like Johnson, Raab and Javid have said they would not rule out a "no-deal" Brexit.
"This campaign is just getting started, and we've got a good base to build on," Raab tweeted after the vote.
Hunt and Gove are against leaving on no-deal terms in October. Hancock and Stewart are against leaving on no-deal terms in any eventuality.
"I now want to make sure that we have a proper debate about ideas," Gove said.
The two candidates most keen on taking Britain out of the EU without a deal were eliminated.
McVey was pursuing a no-deal Brexit, arguing that the agreement May struck with Brussels keeps Britain too closely tied to the EU, while Leadsom wanted a managed no-deal departure.
Harper had argued that an extension would be needed beyond the current 31 October deadline to secure a deal.
The battle will now be on between the remaining seven candidates to scoop up the trio's 20 votes.
Some MPs may tactically switch their secret votes to ensure particular candidates they dislike get knocked out.
Seven down to two
Conservative MPs will keep whittling down the contenders until a final two remain.
Grassroots party members then pick the winner.
Assuming Johnson does not lose support, his tally is above the 105 votes required to secure a place in the last two.
"The question is which one of us is going to go against Boris," said Stewart.
The candidates face their first live television debate on Sunday in a 90-minute programme on Channel 4.
Following Tuesday's second round, in which at least one candidate must drop out, further rounds of voting are scheduled for the rest of the week.
The party hopes to be down to the last two by the end of 20 June.
The final two then do more than a dozen hustings around the country before the 160,000 Conservative party members who choose their favourite in a postal ballot.
The result will be announced in the week beginning 22 July.