lawmakers in the race to replace Boris Johnson as prime minister, but his two remaining rivals were closing the gap, leaving the race wide open.
In a vote among Conservative Party members of parliament, Kemi Badenoch, a former equalities minister, was knocked out, leaving Sunak, Foreign Secretary Liz Truss and Penny Mordaunt, a junior trade minister, as the remaining candidates.
Lawmakers will eliminate one more before the governing party's 200,000 members choose their new leader, who will automatically become prime minister.
Unlike in 2019, when Johnson was a clear favourite going into the contest, the result is more difficult to forecast, with polls of party members suggesting Sunak would lose to whoever is chosen to face him.
Since Johnson said he would resign earlier this month after his scandal-ridden administration lost the support of many Conservatives, the race to replace him has become increasingly ugly with the contenders trading barbs and challenging records.
Mordaunt just held onto second place and thanked colleagues for their support.
"We are so nearly across the finish line. I am raring to go and excited to put my case to members across the country and win," she said in a statement.
Sunak, Truss and Mordaunt have presented policy offerings to try to add momentum to their campaigns, trying to move the focus away from pledges on tax cuts, at a time when Britain's flagging economy has left people with the tightest squeeze on their finances for decades.
Sunak, whose resignation as finance minister helped trigger Johnson's downfall, said he would implement harsher sentences for criminals who fail to attend court and would crack down on gangs that groom girls and young women for sex.
"It will be my top priority in government to keep the British public safe - and I will do whatever it takes to make that happen," he said in a statement.
