Crin Antonescu, leader of the liberal PNL party which came third in the presidential poll with 20.2%, said his party would help socialist (PSD) candidate Mircea Geoana, who finished second, to defeat president Traian Basescu.
Basescu came first in Sunday's poll with 32.43% of the vote, while Geoana came second with 31.16%.
Antonescu said he would never collaborate with Basescu's centre-right PDL party. Relations between PNL and PDL suffered when Bascescu sacked PNL leader and Prime Minister Calin Popescu Tariceanu in 2008, after a feud that had lasted several years.
According to former Romanian President Emil Constantinescu, relations between Basescu and Tariceanu deteriorated after the latter had alleged that the president was a member of Securitate, the powerful communist secret police.
Socialist candidate Mircea Geoana, a former foreign minister, praised Antonescu for the "mature and dignified way in which he presented his positions".
The Romanian press reports today (24 November) that the PSD leadership will decide whether to launch negotiations with the PNL in view of future political cooperation.
Journalists asked Geoana whether the country's next prime minister would be Klaus Johannis, the popular mayor of Sibiu. Geona answered that he would indeed designate Johannis, who represents the small Democratic Forum of Germans in Romania, as prime minister were he to be elected president.
Geoana also deplored electoral fraud (EurActiv 23/11/09), for which he blamed Basescu's camp.
"It's a pity that 20 years after the Romanian Revolution, the Romanians are still deprived of free and fair elections," the PSD leader said.
The Romanian Revolution was a week-long series of violet riots and fighting in December 1989 which toppled the dictatorship of Nicolae Ceausescu. After a parody of a trial, Ceausescu and his wife were executed.