The audience loved her. Her song had all the hallmarks of being a hit at Eurovision, the flamboyant European song contest with a cult following. The tune had romance and easy lyrics, and the singer was accompanied by dancers and had a strobe-lit stage act.

The singer, Anna Korsun, whose stage name is Maruv, was on track to represent Ukraine at the Eurovision final in Tel Aviv in May. But now her chances have been derailed in an apparent geopolitical dispute after officials questioned her patriotism and her decision to tour Russia.

At the national finals last Saturday in Kiev, the Ukrainian capital, Ms. Korsun faced an unusual grilling from the jury. Jamala, the 2016 Eurovision winner from Ukraine whose full name is Susana Jamaladinova, began by questioning Ms. Korsun’s coming tour.

Then she pretended to be a journalist in Tel Aviv and asked a surprising question in English: “Crimea is Ukraine?”