MOMBASA, Kenya — Fireworks popped and confetti rained down in the seaside city of Mombasa when Kenya’s president inaugurated the country’s new railway — designed, funded and built by China.

President Uhuru Kenyatta proclaimed that the new train would connect the port in Mombasa to the neighboring country of Uganda, create jobs and help transform Kenya into an industrialized, middle-income nation.

“This is a very historic moment,” President Kenyatta, waving a giant Kenyan flag, told the gathering of Kenyan and Chinese officials. “We should be proud.”

That was five years ago. The railway has since turned into a fiasco, the target of lawsuits, criminal investigations over corruption and resentment by environmentalists and displaced workers in the trucking industry.

Now, it’s a hot-button issue in the closely contested election on Tuesday and part of a broader debate about China’s expanding role in Kenya. China initially financed the railway as part of its trillion-dollar Belt and Road Initiative, which aimed to expand China’s economic and political clout by funding new ports, roads and railways globally. But China balked at financing the last section of the Kenyan railway — the connection to Uganda — as some African countries struggled to repay their debts.

Both leading candidates in the campaign to pick Mr. Kenyatta’s successor — William Ruto and Raila Odinga — have seized on the railway’s troubles, promising to reassess its operations, while also trying to distance themselves from the project.