Malians voted Sunday in a second round of voting for a post-coup president. Keita took more votes than any other candidate during the first round in July, though he didn't clear the majority needed for an outright win.
Rival candidate and former Finance Minister Soumaila Cisse said on his official Twitter account late Monday: "Keita, future president of Mali."
No official results were published as of Tuesday.
Keita took 39.2 percent of the first round of voting in July, besting Cisse's 19.4 percent.
Keita campaigned in defense of Malian honor, saying the January military intervention by former colonial power France was a national embarrassment. Cisse campaigned for reconstruction of a country divided when al-Qaida and foreign fighters seized territory in the wake of a 2012 coup.
The U.N. peacekeeping mission in Mali said there were no major incidents involved with the Sunday elections. It said heavy rains were to blame for many of the problems during the voting process in most parts of the country.
A Keita profile in a report Tuesday from the BBC said he's favored by moderate Islamic leaders and has the support of the military leadership that toppled the government last year.