ISTANBUL (AP) — Supporters of a pro-Kurdish party in Turkey are planning to rally for local elections that will test the Turkish president’s popularity.

The Peoples’ Democratic Party, or HDP, is holding the rally Sunday in Istanbul amid a polarized race for municipal seats and a crackdown on its members by the government for alleged links to outlawed Kurdish militants considered terrorists by Turkey and its Western allies. Party lawmakers and mayors have been jailed.

The party has fielded candidates for the March 31 vote in Turkey’s predominantly Kurdish southeast but is sitting out critical races in Turkey’s major cities, including Istanbul and Ankara. That way it aims to send HDP votes to Turkey’s main secular opposition party to help challenge Turkish President Recep Tayyip Erdogan’s ruling party.

Millions of ethnic Kurds will vote in the March 31 election.