Security is tight in Togo ahead of Sunday's first parliamentary elections since the death of Gnassingbe Eyadema, who had ruled for 38 years.
Mr Olympio survived an assassination attempt in 1992
Presidential polls after his death in 2005, which his son won, erupted into violence and hundreds of people died.
The party of veteran opposition leader Gilchrist Olympio is taking part for the first time in 17 years.
Mr Olympio has been drawing crowds in Eyadema's northern stronghold where he survived a 1992 assassination attempt.
After his election two years ago, President Faure Gnassingbe oversaw an accord under which opposition parties are represented in the government, paving the way for Sunday's elections.
Correspondents say security is tight for the polls: a special force of 3,500 election police has been created and 100 West African military observers will also be on duty.
TOGO ELECTION IN NUMBERS
81 seats in national assembly
Polls open 0700GMT-1700gmt
Mr Olympio, who has returned from exile to campaign, has said the Togolese are ready for change and promised his Union of Forces for Change (UFC) would win "in all corners of Togo".
Also competing is the Action Committee for Renewal (CAR), the party of another notable opposition figure, Yawovi Agboyibo.
Mr Agboyibo was imprisoned by Gnassingbe Eyadema but was installed as prime minister when Faure Gnassingbe incorporated opposition members into his government.
With two strong opposition parties in the running correspondents say that for once the ruling Rally of the Togolese People (RPT) is not expected to have everything its own way.
The former French colony was controlled for nearly four decades by Gnassingbe Eyadema and his family.
Faure Gnassingbe has held out a hand to the opposition
On his sudden death, the army installed his son Faure Gnassingbe as president, an unconstitutional move that sparked violent protests.
Although he stood in presidential elections in April that year, the poll was condemned as rigged.
Togo's lack of democracy and poor human rights record under the late president led to a freeze on aid by the country's biggest donor, the European Union in 1993.
If Sunday's election is deemed free and fair by the more than 3,000 national and international observers monitoring the poll, it is expected to lead to improved relations, aid and trade.
As Kissy Agyeman, Africa analyst at research group Global Insight, told the Reuters news agency: There is now "a real opportunity to put Togo back on the right footing on the international stage".
Presidential elections are due in three years.