By Maximiliano Rizzi and Sarah Marsh
BUENOS AIRES (Reuters) - Argentina's opposition challenger Mauricio Macri kicked off the campaign on Monday to win over supporters of those candidates eliminated from the presidential election, in a bid to win the run-off against the ruling party hopeful next month.
Macri, the pro-business Buenos Aires mayor, stunned the ruling party on Sunday by winning 34.3 percent of the vote, far more than pollsters had predicted him to win. The news boosted Argentine financial assets on Monday, with one bond hitting a record high.
With returns in from 97.2 percent of polling stations on Monday, the ruling Front for Victory's candidate Daniel Scioli, who had been predicted to win by a strong lead, was only slightly ahead on 36.9 percent.
The two men now face a tight race with everything to play for in the run-off on Nov. 22.
This election will shape how Argentina, Latin America's third largest economy, will tackle its economic woes such as double-digit inflation, precariously low foreign reserves and a sovereign debt default.
"Argentina needs a change and we are ready to make that happen," Macri told a news conference on Monday, calling for those Argentines who voted for third-ranked Sergio Massa, who got 21.3 percent of the votes, and other candidates in the first round of the election to back him in the run-off.
"We are here to represent you, we are here with humility, with responsibility ... and we ask you to accompany us."
Scioli, backed by outgoing leftist President Cristina Fernandez, is running on a platform of "gradual change" and has promised to maintain her popular welfare programs while Macri advocates moving quickly to open up the economy.
He has vowed to start dismantling protectionist currency and trade controls on his first day in office if he wins. Fernandez will hand over to her successor on Dec. 10.
Argentine assets rose across the board on Monday, buoyed by the news of Macri's strong showing, with the defaulted 2038 euro-denominated issue hit a record high of 56.167 cents.
Macri is also favored by investors for promising to free up the economy and conduct more investor-friendly policies. He is also the candidate seen as most likely to reach a deal with a group of "holdout" creditors whose suit over bonds defaulted on by Argentina in 2002 caused a new and ongoing default last year.
"If Macri wins, which is a very strong likelihood ... we have a very interesting growth cycle ahead in Argentina," said Roberto Lampl, Head of Latin American Investments at Alquity Investment Management.
Lamp said that even if Macri won, the road to growth would not be smooth as Argentina needed to devalue the currency, reach a deal with holdouts and address the fiscal deficit.
"Nevertheless, there are hundreds of billions of dollars of savings of wealthy Argentines outside of Argentina, ready to invest in their beloved country," he said.
Scioli was set to give a news conference at noon (1500 GMT).
(Additional reporting by Juliana Castilla in Buenos Aires and Karin Strohecker in London Editing by W Simon)