German Chancellor Angela Merkel and her poll rival, centre-left Peer Steinbrueck, are due to take part in their only televised election debate.
The event is seen as the Social Democrat (SPD) leader’s biggest chance to claw back Angela Merkel’s lead in the opinion polls before this month’s vote.
Although Angela Merkel’s conservative bloc is expected to win, her coalition partners are faring poorly.
The 90-minute debate starts at 18:30 GMT and will be aired on main channels.
With three weeks to go before the September 22 vote, the two candidates will be grilled by four journalists before an estimated TV audience of up to 20 million.
Peer Steinbrueck will face the first question and Angela Merkel will have the final answer, with each answer limited to 90 seconds.
German Chancellor Angela Merkel and her poll rival, centre-left Peer Steinbrueck, are due to take part in their only televised election debate
So far, there have been few campaign issues that have exposed major policy differences between the two figures and the parties have focused on their personalities.
Peer Steinbrueck is often witty but prone to gaffes, while Angela Merkel often seems less than comfortable in the cut and thrust of live debate.
The TV duel may shift enough opinion to alter the election result.
Peer Steinbrueck, 66, served as finance minister under Chancellor Angela Merkel when his SPD party was in a “grand” coalition with her Christian Democrat (CDU) after the 2005 election. But he has refused to enter a similar power-sharing deal.
The pro-business Free Democrats (FDP), currently part of the coalition, are widely expected to perform badly in the polls.
However, an opinion poll on Friday gave Angela Merkel’s conservative bloc 41% of the vote, which might enable her to stay in power with the FDP. Peer Steinbrueck’s Social Democrats were trailing on 26%.
If Peer Steinbrueck does narrow the gap, Angela Merkel, 59, is likely to remain chancellor but the two parties would be forced to consider rebuilding a coalition.
Tony Abbott, the favorite to win next month’s Australian general election, has launched his campaign.
The conservative opposition leader has vowed to control government spending and build a stronger economy by putting “bulldozers on the ground and cranes into our skies”.
Opinion polls show Tony Abbott is poised to end six years of Labor rule.
Earlier this week, Tony Abbott faced electoral rival and PM Kevin Rudd in a second election debate.
Tony Abbott, the favorite to win next month’s Australian general election, has launched his campaign
Addressing a major rally of his Liberal Party in the city of Brisbane, eastern Australia, on Sunday, Tony Abbott said the country could not afford another term under the governing centre-left Labor.
“We’ll build a stronger economy so everyone can get ahead… I hope to be an infrastructure prime minister who puts bulldozers on the ground and cranes into our skies,” he said.
The first debate between the two election rivals on August 11, where Kevin Rudd had been expected to shine, was seen as a draw.
It remains unclear whether there will be a third debate.
Labor has switched prime ministers twice during the time it has been running the country.
Barack Obama has hit out at Republican Mitt Romney during a feisty 90-minute encounter in the second of three presidential debates.
Barack Obama – widely perceived to have lost their first encounter – came out swinging in New York on the economy, tax and foreign policy.
But the former Massachusetts governor accused Barack Obama of broken promises and a record of failure.
They will meet for a final pre-election debate in Florida on 22 October.
As he battles for a second term, the Democratic president has been trying to hold on to dwindling leads in the nine key swing states that are expected to decide the election on 6 November.
In the town hall-style forum at Hofstra University on Long Island, both men freely roamed the stage, circling, interrupting and at times heckling one another as they took questions from an audience of 80 undecided voters.
The moderator, CNN’s Candy Crowley, often had to intervene to keep order between the rivals as each fought to make his point.
Barack Obama set the tone from his first answer, when he contrasted his own bailout of the US car industry with Mitt Romney’s position that auto-makers should have been allowed to go bankrupt.
The president forcefully accused Mitt Romney of inconsistent positions, while claiming that his challenger could only offer a “one-point plan… to make sure the folks at the top play by a different set of rules”.
Mitt Romney meanwhile hammered away at the president’s record on the economy, blaming him for unemployment of 20 million Americans and bloated federal deficits, insisting the country could not afford another four years with Barack Obama at the helm.
In one of the most scathing exchanges, they bickered over last month’s attack on the US Libya consulate that left four Americans dead.
Mitt Romney suggested the Obama administration may have attempted to mislead Americans over whether it was a terrorist attack.
But the president said it was “offensive” to suggest that he had played politics on such a grave issue.
He countered that it was the Republican who had tried to turn a national tragedy to his advantage by releasing a partisan press release about the deadly assault.
As the debate progressed, both candidates made repeated and impassioned pitches to America’s middle class.
Barack Obama said he had cut taxes for middle class families and small businesses over the last four years.
But he said that if America was serious about reducing the deficit, the wealthy would have to pay a little bit more.
“Governor Romney and his allies in Congress have held the 98% hostage because they want tax breaks for the 2%,” said Barack Obama.
In his final answer he responded to an assertion by Mitt Romney that the Republican would represent “100% of Americans” by bringing up Romney’s secretly recorded remarks at a fundraiser in May.
In those remarks the challenger dismissed 47% of Americans as government-dependent tax avoiders who take no responsibility for their lives.
“When he said behind closed doors that 47% of the country considers themselves victims who refuse personal responsibility – think about who he was talking about,” the president said.
Barack Obama said voters had heard no specifics on Mitt Romney’s “sketchy” tax plan apart from eliminating Sesame Street’s Big Bird and cutting funding for Planned Parenthood, a family planning organization Republicans say promotes abortion.
“Of course it adds up,” Mitt Romney said of his tax plan. He cited his experience balancing budgets in business, while running the 2002 Olympics and as governor of Massachusetts.
Barack Obama ticked off a list of achievements over the last four years: tax cuts for the middle class; ending the war in Iraq, killing Osama Bin Laden; helping the auto industry, as well as healthcare reform.
But Mitt Romney said the last four years had not been as rosy as the president would like to portray, saying the president had made pledges to deliver unemployment of 5.4%, an immigration plan, and to cut in half the deficit, but had met none of them.
“The president’s tried, but his policies haven’t worked,” said Mitt Romney.
One of the sharpest exchanges of the debate came when the pair clashed over former private equity chief Mitt Romney’s wealth.
Mitt Romney was defending his investments in China through a blind trust when he asked Barack Obama if he had looked at his own pension. He said Barack Obama would find investments in China in his retirement plan, too.
Barack Obama countered that he did not check his pension that often, adding: “Because it’s not as big as yours.”
Another fragment of the debate prompted a flurry of social media comment.
Arguing that he supports equal opportunities for women, Mitt Romney said he once had “binders full of women” candidates for cabinet jobs when he was Massachusetts governor.
The third and final presidential debate is scheduled for 22 October in Boca Raton, Florida.