Japan's upper house election on Sunday could shake up politics, with rising prices and a populist party gaining ground. What’s at stake for PM Ishiba and Japan’s future?

Japanese voters could unleash political turmoil as they head to the polls on Sunday in a tightly contested upper house election, with rising prices and immigration concerns threatening to weaken Prime Minister Shigeru Ishiba's grip on power.

Throughout the spring, Ishiba battled to reach a deal on the government’s budget and to assuage concerns among the public about the rising cost of living. But a weak political base is not Ishiba’s only problem.