At the helm of the small West African country for nearly 20 years, Faure Gnassingbe succeeded his father, Gnassingbe Eyadema, who ruled for almost four decades.
Critics say the political dynasty's hold on the small West African nation will be extended by the reform.
People in the streets of the seaside capital, Lome, were split over the election, the role of Togo's leader, and who it should be.
Building painter Komlan Gato said he hoped the vote could usher in a new leader but was unsure about the fairness of the ballot.
"I am certain that if these elections are transparent, there will be change in this country. We are tired of seeing the same family in power," he said.
"I was born in January 1970, and I only know the Gnassingbe family in power."
The reform, adopted by lawmakers on April 19, makes the president's post a largely ceremonial one.
The president will now be elected by parliament and not the people for a four-year term.
Power will reside with the president of the council of ministers, a sort of super-prime minister who happens to be the leader of the majority party in the new assembly.
If the ruling Union for the Republic (UNIR) party -- which has an overwhelming parliamentary majority -- wins on Monday, Gnassingbe can assume the new post.
Critics say that will allow him to skip presidential term limits. As president he would have been able only to run for one more five-year term in an election next year.
The opposition boycotted the last elections in 2018, citing irregularities. But they have asked supporters to turn out massively to challenge the UNIR's stranglehold on power.
"The youth are desperate. The country is poorly managed and we are tired of the system in place," said trader Ayaovi Sohou, 32.
Bernado Agbve, a baker, 28, called on the Independent National Electoral Commission to "publish results from the polls: good results and not fictitious results."
Gnassingbe has been reelected four times since being put in power in 2005 by the military to succeed his father after his sudden death. Each of the votes was rejected as a sham by the opposition.
'Much remains to be done'
For Elvire Atchou, 38, an accountant in an insurance company, Gnassingbe should be allowed to continue.
"Togo is changing, let President Faure Gnassingbe continue the major projects: construction of roads, schools, health centers," she said, adding, "I know that much remains to be done."
With the country facing the risk of spillover from jihadist conflicts in the Sahel to its north, security and stability are key concerns.
Nutsugan Koffi, 25, a taxi driver, said Gnassingbe should be allowed to stay as long as Togo is stable.
"There is peace in Togo. It is very important for the development of a country. President Faure Gnassingbe can remain at the head of this country as long as possible, that does not bother me, provided that we are comfortable," he said.
"The only thing that young people expect is employment."
The constitutional reform also means Togo can shift away from presidential elections that have often sparked violence, he said.
All the presidential elections since the start of democracy in 1990 have been contested by the opposition, often with waves of violence, notably during the April 2005 vote.
Violence left at least 105 and perhaps more than 800 people killed, depending on figures from the government or from the opposition. The United Nations estimated at the time that there were between 400 to 500 deaths.
Leaders of opposition parties and civil society organizations brand the reform an "institutional coup" tailor-made to keep Faure in power.
They have announced "large-scale actions" without giving details, though the last attempt to bring supporters to the streets was quickly banned and blocked by authorities.