Poland's path to narrowing its fiscal deficit, maintaining its credit ratings and keeping investors on board looks more difficult following conservative nationalist Karol Nawrocki's presidential election triumph.

Warsaw’s liberal mayor and his insurgent populist challenger are locked in a dead heat as they fight for the presidency of Poland, exit polls projected after Sunday’s head-to-head vote, leaving the country tilting between two wildly different political futures.

Nationalist Karol Nawrocki's victory in Poland's presidential election deals a major blow to pro-EU premier Donald Tusk and looks set to rattle Brussels.

The result is expected to shift Poland toward a more populist and nationalist approach. The spectacular turnaround following earlier prediction is reminiscent of the 2016 Brexit referendum.

Here’s what to know about Poland’s presidential runoff, which sets up a showdown between the governing party and resurgent nationalists.

“In the first round of the election, you had only 60 percent of people voting for the two strongest candidates,” Buras said. “That was the lowest joint result of the two top candidates in the history of Polish presidential elections. Which means many ...