Hundreds of people booed President Abdoulaye Wade as he voted at his home precinct on Sunday.
Mr. Wade has angered many Senegalese by trying to extend his 12-year rule of the west African nation.
Opponents say his bid is unconstitutional following a reform he signed into law in 2001 that limits presidents to two terms.
The presidentially-appointed Constitutional Court ruled last month the reform did not apply to Mr. Wade because it came into effect while he was already in office.
Thirteen other candidates are running against President Wade including two who have served as prime minister during his rule.
The voting was preceded by weeks of unrest in which protesters, throwing rocks and erecting fiery barricades, clashed with police who used tear gas and rubber bullets. At least six people were killed in the protests.