Martin Schulz, the leader of the Social Democratic Party and a former European Parliament president, is seen as the underdog in the race for Germany's top job.
But he has remained upbeat during the campaign ahead of the 24 September vote, insisting his party can close the gap and unseat his centre-left rival, Chancellor Angela Merkel , after 12 years in power.
Here is a look at his career ahead of the German federal parliamentary elections.
Who is he?
Mr Schulz, 61, has spent most of his career - 23 years - in the European Parliament, where he served as president from 2012 until he resigned this year to contest the German election.
His highest elected position in Germany was as mayor of the small western town of Wuerselen.
He was born in western Germany in 1955 as the fifth child of a policeman and housewife, who he described as "simple and very decent people". At school, he had been hoping to become a professional footballer but was struck down by injury.
He fell into depression and heavy drinking but managed to pull himself back together and, rather than going to university, trained as a bookseller. He opened a bookshop before becoming a member of the European Parliament in 1994.
In 2003, he clashed spectacularly with former Italian prime minister Silvio Berlusconi. During a pointed exchange between the two in the European Parliament, Mr Berlusconi suggested Mr Schulz should audition for the role of a "kapo" - a concentration camp guard.
The incident caused widespread outrage for Mr Berlusconi and a diplomatic rift between the pair. In Germany, it also helped make Mr Schulz a household name.
"I felt humiliated," Mr Schulz recalled years later, according to the Financial Times.
The year he became the European Parliament chief, 2012, he collected the Nobel peace prize on behalf of the bloc, along with other EU officials.
What can we expect?
Mr Schulz has spent almost all of his adult life as a member of the Social Democratic Party (SPD). During the campaign he reiterated his calls for free education, more investment such as in nursing care and schools as well as qualification programmes for the unemployed.
He vowed to close the "intolerable pay gap" so men and women in both eastern and western Germany get the same amount of pay for doing the same work, and has pledged to get rid of US nuclear weapons stationed in Germany.
He visited Italy to discuss a European-wide approach to the refugee crisis, opposes the idea of a cap on refugees, and has sought for the most part to keep the issue of Mrs Merkel's handling of the refugee influx outside of the campaign.
As European Parliament President, Mr Schulz has been advocating a bigger role for the EU's legislative body, and has been highly critical of Brexit and the British Conservative Party.
"You should not take a whole continent as a hostage for a party's internal struggle," he said last year.
He said the British Government expected a different outcome from the referendum and was not prepared for the result, saying: That shows you should never play with fire."
Who is backing him?
Mr Schulz has consistently trailed in the polls but is hoping his "man of the people" appeal and Ms Merkel's difficulties over her handling of Europe's refugee crisis might give him a chance.
With the economy performing well and unemployment at a record-low, however, Germans may have little appetite for political change.
He has acknowledged his party suffered two "very, very difficult defeats" in recent regional elections, but insisted the national contest could swing his way because many voters are still undecided.
Under Germany's proportional representation system, if the Social Democrats surprisingly emerged as the largest party, they could try to form a coalition with the Greens and a far-leftist Left party, which he has not ruled out.
He could also form a coalition with the Green and the business-friendly Free Democratic Party.
Did you know?
Mr Schulz, who is married and has two children, has been teetotal since 1980. A polyglot (speaker of several languages), he is said to be an avid reader from his days as a bookseller, especially of historical biographies.
He told the FT that he writes a diary every day.