Hardcore supporters of the militarily vanquished Liberation Tigers of Tamil Eelam (LTTE) in the West wanted Tamils living in the north and east of the island to stay away from the Jan 8 election.
According to them, both Rajapaksa and his main challenger Maithripala Sirisena were Sinhalese-Buddhists, and electing either made no sense from the Tamil point of view.
This was the same line the LTTE took in the 2005 presidential election when it ruled vast areas of Sri Lanka's north and east.
The LTTE then said that there was nothing for the Tamil community to choose between Rajapaksa and Ranil Wickremesinghe though the latter had signed a peace deal with the Tamil Tigers in 2002. One was a cobra, the other a python, the LTTE had argued.
Fearing the LTTE's wrath, Tamils living in its sprawling zone across the north and east of Sri Lanka boycotted the polls, helping then prime minister Rajapaksa to narrowly edge past Wickremesinghe and become president.
That razor thin win, everyone later admitted, was possible only because of the LTTE-ordered Tamil boycott. Otherwise Wickremesinghe, who would have got most Tamil votes, would have worsted Rajapaksa, albeit narrowly.
This time, minus the LTTE, the Tamils refused to buy the same old argument. The Tamil National Alliance (TNA), the main Tamil party in parliament which in 2005 acted like the LTTE's mouthpiece, decided to support Sirisena, who became the joint opposition candidate.
This irked the pro-LTTE lobby, dominantly present in Western countries. Tamil diaspora leaders in the LTTE mould charged the TNA with betraying the Tamil people. A handful of TNA personalities took the same line.
The Indian government advised the TNA leadership not to boycott the presidential election.
In any case, there was widespread anger within the Tamil masses in the north and east of Sri Lanka over the way thousands among them were killed in the final stages of the war that crushed the LTTE in May 2009.
The fact that the Rajapaksa brothers who governed Sri Lanka did nothing tangible to heal their wounds combined with the TNA's call to defeat Rajapaksa sent hundreds of thousands of Tamils to polling centres Jan 8.
That single act sealed Rajapaksa's fate and propelled Sirisena to power.
In the final analysis, Rajapaksa still managed to retain, by varying margins, most Sinhalese-dominated areas in the western, central and southern parts of Sri Lanka.
Support for Sirisena was so overwhelming in the north and east -- populated overwhelmingly by Tamils as well as Tamil-speaking Muslims -- that it punctured whatever advantage Rajapaksa gained in the Sinhalese belt.
Interestingly, two other places where Sirisena won heavily were Nuwara Eliya, home to tens of thousands of Tamils of Indian origin, and cosmopolitan Colombo where Tamils and Muslims live in large numbers.
Had the pro-LTTE line prevailed, Rajapaksa would still be the president of Sri Lanka.