Official campaigning for Spain's December 20th general election begins Friday with conservative Prime Minister Mariano Rajoy facing a stiff challenge from three younger rivals in the tightest race in decades.
With some polls showing that more than one in five potential voters are still undecided less than three weeks before the election, it is impossible to predict who will win, said Manuel Mostaza, the operations director at the Sigma Dos polling firm.
"These are the most volatile elections ever," he told AFP.
Three party leaders who were unknown during the last general election in 2011, which Rajoy's Popular Party won by a landslide, have emerged during Spain's sharp economic downturn and are well positioned as the election nears.
The three - rising star Albert Rivera, 36, from the centrist Ciudadanos party, the Socialists' Pedro Sanchez, 43, and far-left Podemos candidate Pablo Iglesias, 37 - set out their positions on Monday in a two-hour live Internet debate hosted by daily newspaper El Pais.
Rajoy, 60, declined to take part and attended a one-on-one televised interview instead on Telecinco, Spain's most-watched television station.
His Popular Party has been worn down by corruption scandals, austerity measures and the unemployment rate which is falling but still stands at 21.2 percent, the highest in the eurozone with the exception of Greece.
The Popular Party holds a narrow lead ahead of the polls with 27.1 percent support, according to Sigma Dos, compared to the 44.6 percent it won during the last election.
Ciudadanos is in second place with 23 percent support, followed by the Socialists with 20.2 percent and Podemos with 16.2 percent.
Another poll by Metroscopia pointed to an even closer contest. It put support for the Popular Party, the Socialists and Ciudadanos within a hair's breadth of each other at 22 percent with Podemos, a close ally of Greece's ruling Syriza, in fourth place with 17 percent support.
The surveys indicate no party will secure a parliamentary majority, with Ciudadanos likely to emerge as kingmaker.
Ciudadanos has criticised both the Popular Party and the Socialists - Spain's two main parties which have dominated politics since the country returned to democracy following the death of dictator Francisco Franco - and it is not clear which formation it would support.
Economy in focus
The November 13th jihadist attacks in Paris and a strong independence drive in the northeastern region of Catalonia, where the regional assembly passed a resolution last month calling for secession from Spain, have made national security and unity campaign issues.
Rajoy will debate Sanchez, who took the helm of Socialists last year, on December 14th. He will not debate the leaders of Ciudadanos or Podemos since those parties are not represented in parliament, according to the Popular Party.
Podemos did not exist during the last election and Ciudadanos only operated in Catalonia at the time, not at the national level.
Rajoy has made economic recovery one of the mainstays of his campaign for re-election after Spain in 2014 came out of five years of recession or zero-growth.
The government predicts the economy will expand by over 3.0 percent this year.
"We are starting to have more resources," Rajoy said during the television interview on Monday.
Public workers in November received part of an annual Christmas bonus that was cut in 2012 and will receive another part later this month.
Rajoy has vowed to cut income tax and create two million jobs over the next four years if his party is re-elected.
He plans to focus his campaign on the offer of the "experience" of a "competent" team and "security", his campaign chief Jorge Moragas told reporters.
But opponents of the Popular Party say many of the jobs that have been created are short-term or badly paid.
Rivera said during the debate 90 percent of the new jobs created under Rajoy's watch were "garbage contracts" while Sanchez said "one in four contracts in our country last less than one week".
By Michaela Cancela-Kieffer