“I’m not a sore loser; I’m a democrat,” Mr. Odinga said in an interview last week. “If I do lose, I’d like to be able to declare the winner fairly.”

The unrest pushed Mr. Odinga out of the country. He left Kenya on Sunday night, according to Salim Lone, a longtime adviser to Mr. Odinga and his political party. He is now in Zanzibar, off the coast of mainland Tanzania, Mr. Lone said.

The Supreme Court matter had centered on the fairness and constitutionality of the latest vote. Petitioners had claimed that Kenya’s election commission had not acted impartially and had not followed the Constitution properly when it organized the Oct. 26 election, which was thrown into turmoil when Mr. Odinga withdrew from the race just weeks before ballots were to be cast. He had argued at the time that the process could never be free and credible.

Then, one week before the vote, an election commissioner fled the country, citing threats to her life, and resigned. The chairman of the commission said political interference by both parties threatened the credibility of the vote. And on the eve of the election, the Supreme Court was unable to hear a last-minute challenge over the process, because too few judges showed up.

The court did not provide reasons for its latest ruling, citing time constraints, but said it would issue a full judgment within 21 days. Kenya’s election commission has said that Mr. Kenyatta garnered 7.5 million votes in the Oct. 26 election, with a turnout of 38 percent. The opposition, however, disputes both figures.