The summit from November 15-17 is controversial. Rajapaksa, now in his eighth year of power, is much reviled - at least in the West.
The chief charges against him are serious: that he ignored, condoned or even encouraged war crimes committed by Sri Lankan troops in the final bloody phases of the campaign to crush the brutal Liberation Tigers of Tamil Eelam (Tamil Tigers); that he has again ignored, condoned or possibly even ordered a wave of repression directed at those who contest his or his Government's authority; that he has made no serious effort to reach out politically to Sri Lanka's Tamil minority; that he aims to ensure that his family's grip on the island nation is without challenge for decades to come.
In short, it is alleged that under his rule Sri Lanka is becoming a nasty, authoritarian quasi-rogue banana republic.
If there is some truth in many of the charges, the reality, like the man, is more complex than appearances suggest. In person, Rajapaksa is more avuncular than ogre. Tall, heavy-set, with an astonishing bouffant as solid, glossy and black as polished coal, he exudes the hearty bonhomie of the rugby player he once was.
He remembers names, slaps backs, happily strips to the waist when he visits temples, and makes sure his guests, even journalists who have come to grill him, have been offered a cup of tea. Such gestures reveal a canny politician with a carefully cultivated folksy style.
Almost all Sri Lanka's post-independence leaders have been smooth, English-speaking, often educated abroad, and from Colombo or its environs. Rajapaksa, a small-town lawyer, is thus very different, even if he does come from a political family.
One problem for his critics is that, though elections are marred by intimidation, violence and the misuse of state resources, few deny that Rajapaksa's successive poll victories reflect a genuine mandate. Even his opponents in Colombo admit that he remains without a serious local political challenger. His heartland is rural, conservative, Buddhist and dominated by the Sinhalese majority.
It was these voters that, as a 24-year-old novice politician armed with a law degree and a famous father, he won over to enter Parliament for the first time in 1970. The same voters backed him in 2005 when, after a year as prime minister, he stood for president, and still back him now. Part of the dislike, and the fear, that Rajapaksa inspires in Colombo's political elite is his unashamed exploitation of his status as a political outsider.
The emotions Rajapaksa inspires in many Tamils, who comprise about 15 per cent of the population, have their source elsewhere. A key election pledge was to end the bitter war against the Tamil Tigers, the de facto government in much of the north, by negotiation. This stance shifted. Here his brother, Gotabhaya, the defence secretary, played a key role, as he would do in the campaign to come. During the 26 years of conflict there had been a number of truces, most recently in 2002. These, the Rajapaksa brothers and the senior military believed, were simply used by the Tamil Tigers to resupply and reorganise. This time the Rajapaksas decided there would be no truce, whatever the international pressure.
The military was expanded hugely. The ceasefire collapsed entirely. Only during the last few weeks of the conflict did the world begin to take notice of events in northern Sri Lanka. As they retreated, the Tamil Tigers took hundreds of thousands of civilians with them.
In a series of interviews last month, non-combatants spoke of chaos, "no-fire zones" that were not respected by the army, and orders from the Tamil Tigers to leave their homes. What is also clear is that the Tigers made little effort to separate combatants from civilians, particularly towards the end of the fighting, when huge numbers, including fighters and the Tamil Tiger high command, were packed into a tiny area between a lagoon and the sea. They may have shot some people who tried to escape.
But the army bombed, shelled and strafed the area indiscriminately, killing the Tigers' leaders but also thousands of civilians.
There are also reports, backed by images shot on soldiers' phones, of large numbers of summary executions of captured rebel cadres and some civilians.
These are the alleged war crimes the UN wants independently investigated - something the Sri Lankan Government has so far failed to do. Rajapaksa has called the allegations "propaganda" and accused the UN of doing the bidding of "big countries" who "bully" little ones.
Since the end of the war other concerns have intensified. There have been scores, some say hundreds, of abductions. Journalists are systematically threatened. Trade unionists and human rights activists receive regular "warnings" or are roughed up. The constitution has been changed to allow Rajapaksa a third term. Dozens of his relatives hold government posts, controlling, according to one estimate, nearly half the state expenditure. A son is being groomed as a successor. There are widespread allegations of graft and an upsurge in sectarian violence.
"It is a situation of total state capture," said JC Weliamuna, a leading human rights lawyer in Colombo.
So far the only invited leader not attending the Commonwealth summit is Canada's Stephen Harper. Britain's David Cameron says "tough messages" are best delivered in person. Rajapaksa will no doubt be his usual bluff and cheery self at the meeting. But if anyone is delivering a tough message, it will be him.
- Observer
