PRAGUE (AP) — Czechs cast ballots on Friday in the second round of voting for a third of the seats in Parliament’s upper house, the Senate.

The current ruling coalition led by Prime Minister Petr Fiala has a clear majority in the Senate though the main opposition group, led by former populist Prime Minister Andrej Babis, has the most candidates advancing from last week’s first round to the runoff for 27 seats in the 81-seat Senate.

The top two finishers in each district faced each other in a head-to-head vote. Babis’ ANO, or YES in English, had 19 candidates advancing to the runoffs, the best first round result for the centrist movement.

Five candidates reached the 50% threshold in the first round to win seats outright, leaving 22 seats to be decided in runoffs.

Parliament’s lower house dominates the legislative process, but the Senate plays an important role in passing constitutional amendments and approving Constitutional Court judges.

The results of the two-day vote will be known later on Saturday.

In a separate vote last week, ANO also dominated Czech regional elections, winning 10 of the 13 regions contested.

In another setback for the ruling coalition, a junior party, the Pirates, said earlier this week that it would leave the Cabinet over Fiala’s decision to fire the party leader. Fiala said he had lost trust in Ivan Bartos’s ability to deal with the problems linked to a new digital system for issuing building permits.

Fiala’s government will retain a majority in Parliament’s lower house, even without the Pirates.