Last January, Sri Lanka’s health minister, Maithripala Sirisena, joined his colleagues in toasting the Chinese New Year at a red-lantern-festooned gala featuring performances of the songs “Love My China” and “Mother Sri Lanka” and hosted by the Chinese Embassy in Colombo, the capital.

But today, with Mr. Sirisena the surprise victor in Sri Lanka’s presidential election, Chinese leaders are likely to be watching with some unease to see if he follows through on a campaign promise to scrap a major Chinese investment project.

China in recent years has become a leading investor and trading partner for the strategically situated island nation, which is roughly 40 miles off the southeastern coast of India. President Mahinda Rajapaksa, who was defeated in the vote, had welcomed Chinese investment. And China, which has been expanding its naval abilities and reach, seemed to have found a good friend in the Indian Ocean. But in the early hours of Friday, Mr. Rajapaksa was forced to admit defeat after results showed he was trailing his former aide.

…Anit Mukherjee, an assistant professor at the S. Rajaratnam School of International Studies in Singapore, said on Friday, “It’s hard to take a guess” on whether Mr. Sirisena will follow through on his promises and cancel the two projects.