Editor's Note: Watch the leadership debate (Foreign Affairs) and post-debate analysis on CNN.com Live: Thursday April 22, 2000 -- 2200 BST / 1500 -- 1700 ET.
London, England (CNN) -- The leaders of the UK's three main political parties will clash again Thursday in the second of three televised debates which have energized the country's general election campaign.
Thursday's debate, which will be broadcast live on CNN International and CNN.com Live, is due to focus on foreign policy with the UK's role in the war in Afghanistan and its position in the European Union likely to dominate the agenda.
Most watchers of last week's opening debate -- the first in British electoral history -- scored the contest as a surprise victory for Nick Clegg of the Liberal Democrats over Prime Minister Gordon Brown, the leader of the Labour Party, and Conservative leader David Cameron.
The Liberal Democrats have long been the outsiders of UK politics but Clegg's performance triggered an unprecedented boost for the party in the polls, with some even putting them in first place.
That has increased the pressure on Brown and Cameron and made the prospect of a "hung parliament," in which no party achieves an overall majority, more likely, according to analysts.
With another debate on the critical issue of the economy and two more weeks of campaigning still to come, Thursday's debate will offer clues as to whether the Lib Dem surge has the legs to last until election day on May 6.
CNN political commentator Robin Oakley said Clegg would be under pressure to prove he is no "one-show wonder" and would face a tougher time from Brown and Cameron, whose strategists are now taking the Lib Dem threat seriously.
"Spin doctors in other parties have conceded that Clegg won that first debate. As a result they and their leaders will now be targeting the Third Man. But cutting him back may not be easy," said Oakley.
"In an age when the expenses scandals of the last parliament left electors deeply contemptuous of parliamentarians, Clegg, as the outsider, managed to convince the audience that he was one of them and not part of a cosy old political machine."
But Oakley said that Clegg faced a tougher job defending his party's policies towards Europe.
As a former lawmaker in the European Parliament leading the UK's most solidly pro-European party, Clegg's background has already been scrutinized by the right-wing and Euroskeptic elements of the British media.
"Cameron, who has taken his party out of the European alliance of mainstream center-right parties, now leads the most Euroskeptic Conservative Party in history and might be able to play that to his advantage," said Oakley.
He said Clegg would likely also face attack by both Brown and Cameron over his party's support for the abolition of the UK's Trident nuclear deterrent system; a stance which, his opponents will likely claim, leaves the Lib Dems open to the criticism that they are soft on national security.
"The interesting thing will be to see how Clegg fares not calling a plague on both the other houses but sticking to his guns on a less than popular policy," said Oakley.
In recognition of Clegg's emergence as a possible kingmaker in a hung parliament, Brown on Wednesday admitted that the election was "wide open" and said that Labour was ready to make common cause with the Liberal Democrats on the issue of electoral reform.
"There is some common ground on the constitutional issues. It is up to the Liberals to respond," Brown said in an interview given to the Independent newspaper.
Clegg, responding in comments to the Daily Telegraph newspaper, called Brown "desperate."
"Brown systematically blocked, and personally blocked, political reform. I think he is a desperate politician and I just do not believe him," he said.