Foreign Sec. Liz Truss and former chancellor Rishi Sunak faced off Mon. night in their first head-to-head debate.

Mon.'s debate, hosted by BBC, was the candidates' first debate since the final round of voting among Conservative MPs.

Sunak won the fifth and final ballot with 137 votes. Truss trailed Sunak with 113 votes. (BBC)

Sunak and Truss largely traded barbs over their divergent tax and spending policies Mon. night.

Sunak accused Truss of promising "£40B of unfunded tax cuts" in her plan: "[That's] £40 billion more borrowing."

Truss responded that the UK's fiscal headroom allowed her to cut taxes, then pay off the UK's debt in "three years' time."

Truss: "There is already headroom of approximately £30B in the budget..."

The environment also took center stage during the debate: Truss said Mon. that she was once a "teenage eco-warrior."

Johnson's long line of scandals also came up during the debate: Truss said Mon. that the party was wrong to oust him.

Truss: "I’m still Foreign Secretary, and I think it’s important that I remain in my post."

Both candidates were also asked if they would let Johnson serve in their Cabinet. Sunak: "The simple answer for me is no."

Sunak: "I think it's incumbent on whoever leads this country to bring our party back together."

Truss: "I very, very much suspect that he would not want a future role in the government..."

Who's favored in the race so far? Per a Thu. YouGov poll, Truss beats Sunak 62% to 38% among 730 party members.

What's the timeline for the race? Ballots are set to be sent out to the party's 160K+ members on Aug. 5. (BBC)

Results from the leadership race are expected to be announced on Sept. 5 at 12.30 pm. (BBC)