BRASILIA, Dec 14 (Reuters) - Years after going head-to-head for Brazil"s top job, leftist former President Luiz Inacio Lula da Silva is seriously considering ex-rival Geraldo Alckmin as a centrist running mate next year, presenting a "unity" ticket for a divided country, according to Reuters interviews. Five sources close to the politicians, who spoke on the condition of anonymity to discuss private matters, told Reuters that both sides are serious about a possible joint ticket, which would put aside two decades of fierce opposition. So far the two have not met to discuss the issue, with the initial courting done by trusted allies on both sides. A dinner between Lula and Alckmin had been set for Dec. 3, but was postponed after details were leaked in local media, four of the sources said. Neither side has publicly confirmed talks have been taking place. The two faced off in a 2006 run-off vote that gave Lula a second term. In 2018, Alckmin ran again for the presidency, falling short of the votes necessary to make it into the second round. An increasingly polarized Brazil has brought them closer, however. Their rivalry harks back to the days of a narrower political spectrum, before the rise of President Jair Bolsonaro and the consolidation of the far-right as an electoral force. For some analysts, it would be a clever marriage. Emblematic of Lula"s skill as a negotiator and veteran statesman, they say the pairing could ease some resistance from Brazil"s business community, which has grown disillusioned with President Bolsonaro, but still distrusts Lula"s Workers Party and its social policies. The idea is straight out of the Lula playbook, according to Creomar de Souza, founder of Dharma Political Risk and Strategy in Brasilia. "In both of Lula"s (presidential) victories, he was on a ticket with a VP who leaned more towards the center-right," Souza told Reuters. "Lula seems to have a firm understanding of the need for someone who can reduce some of the anxieties that the Workers Party triggers in more conservative and traditional parts of society," he added. . Those anxieties are not easily assuaged. Although Lula currently leads the polls, his rejection rates remain around 40%. Supporters highlight Lula"s policies increased investment in social programs that helped lift millions of Brazilians out of poverty, while critics accuse him of overseeing rampant corruption. Prosecutors said they uncovered vast kickback schemes that ran through the heart of government during the 13 years the Worker"s Party were in power. Lula himself was jailed on bribery charges, but the Supreme Court annulled his convictions earlier this year. Lula has always denied any wrongdoing and said the charges were politically motivated. AN UNLIKELY ALLIANCE In Alckmin, a figurehead of one of Brazil"s most traditional political parties and four-term former governor of business powerhouse Sao Paulo, Lula has found an unlikely partner looking to mount his own comeback. Despite Alckmin"s impressive nine-party coalition in 2018, his candidacy fizzled with a fourth-place finish. Now he has a chance to bring his establishment credibility to a big-tent presidential ticket alongside Lula, who holds a healthy double-digit lead over Bolsonaro in recent surveys. "For the markets, it would be an expression of a pragmatic Lula, open to negotiating," said Rafael Cortezos, a political analyst at Tendências Consultoria. For Alckmin, it could be another chance for national influence as he looks to leave behind his Brazilian Social Democratic Party (PSDB), where he has lost clout. "He still hasn"t decided but he"s very enthusiastic. He sees it as an opportunity to help ease tensions in the country," one source close to Alckmin said. "He likes Lula. It wouldn"t be a problem for him." Lula"s team, meanwhile, say the possible pairing shows the leftist"s democratic values and a way to overturn views of next year"s election as a clash between the extreme right and extreme left, a dichotomy that some analysts say favor Bolsonaro. "Let"s get rid of this idea of polarization ... We will unite the country around the constitution," said one source close to Lula. A joint ticket, they said, would be "a sign of that intent."