His dissent is not without consequence: in the run-up to this election he was evicted from his former office, and both he and his deputy were evicted without warning from their homes.
"People should stop thinking it is only the ruling party that has the right to do what it wants... we need to feel free, to express ourselves without fear that you will be evicted from your house or lose your job."
In a Kigali garden, the other opposition candidate, Mpayimana, appears somewhat dazed to be in the race at all as he sits around a table strategising and sipping beer with a small team of advisors.
He was the only one of four independent hopefuls to be allowed to run and is worried that there hasn't even been time to print or put up campaign posters.
"I have only one week to raise awareness among people to support me financially," said the 47-year-old former journalist who spent 18 years in exile in the Democratic Republic of Congo and France, before returning to Rwanda in February to run as an independent.
He is careful not to criticise Kagame but says he would like to "change the mentality of my country to go with the notion of democracy".
Kagame won 2003 and 2010 elections with more than 90 percent of the vote.
Outspoken local journalist Robert Mugabe is one of several observers who see the opposition candidates as a front to appease Western donors and give the impression that democracy is alive and well in Rwanda.
"The real opposition, the people with the real voices cannot be around," he said, referring to those who have been jailed or forced into exile.
Political analyst Christopher Kayumba said Kagame remains popular with Rwandans, who see him as a guarantor of their stability after his military victory brought an end to the genocide.
The ruling RPF also holds overwhelming economic power, with its investment arm Crystal Ventures the biggest private employer in the country, and is omnipresent in daily life.
"Security remains critically important because today we still have people who lived their entire life in war. We only recently had a sustained period of peace," he told AFP.
"There is no way you can compare the stature of president Kagame, the resources of the RPF, with the Green Party. The opposition will be beaten hands down. There is no question about that."