The other candidates - Communist Party leader Gennady Zyuganov, populist nationalist Vladimir Zhirinovsky and the almost unknown Andrei Bogdanov - are forecast to score less than 30 per cent between them.
Unlike Putin and most of his inner circle, Medvedev has no KGB or other security service background, but he is a long-time friend and colleague of Putin, and has pledged to continue his policies.
'No election to rig'
Garry Kasparov, the leader of the Other Russia coalition of parties, told reporters at the central election commission in Moscow that Sunday's poll would not establish whether there was real support for Medvedev.
"I can't tell you if he is popular," he told reporters.
"I warn you against using words like 'popularity' which suggest that there is a democratic process, that he is being tested."
Kasparov said that Russia's leaders had rigged previous elections but this time there was "no election to rig".
Russian officials have been working hard to ensure a high turnout - despite the apparently foregone conclusion - in order to grant Medvedev the legitimacy to rule.
Putin gave a televised speech urging Russians to go to the polling stations on Sunday, underscoring that each person's vote is important.
However, the Parliamentary Assembly of the Council of Europe, which has sent in 25 election observers, has said that the vote "can hardly be considered fair".
Transparency International, an anti-corruption watchdog, and Golos, a Russian election monitoring group, said that the Kremlin had stage-managed the contest through media bias, pressure on regional leaders and the use of state resources.
"In practice the administration is controlling the election," Lilya Shibanova, head of Golos, said.
Medvedev has dominated the state-run media during the campaign with reports on a tour of the country as deputy prime minister running for several minutes at the top of most news bulletins.
Transparency International called this an example of "political corruption" saying the state had effectively funded his campaigning.
A study by the Centre for Journalism in Extreme Situations said Medvedev received 51.5 per cent of election of coverage on state-owned Channel One in January.
However, many of the 109 million Russians eligible to vote do not seem bothered by the charges and seem to support the recommendation made by the incredibly popular Putin.
"Many people support the opposition but many more support the Kremlin, because the other candidates are not suitable for us," Natalya Alekina, a tourist visiting Moscow, told Al Jazeera.
Alexey Volkov, a Moscow resident, said: "People have the opportunity tomorrow to go to the polling station and register their opinion."
Voting is to begin at 8am (20:00GMT) on the Pacific coast of the world's biggest country before rolling 12,000km west to Moscow, and then on to the Baltic Sea territory of Kaliningrad, where it will close at 8pm (18:00GMT) on Sunday.