The main opposition Constitutional Democratic Party of Japan (CDP) won big Sunday night, racking up victories in three key by-elections, including a closely watched race in a district that was long a ruling Liberal Democratic Party stronghold.

The results are a further blow to Prime Minister Fumio Kishida — who concurrently serves as LDP president — and could accelerate talks within the party about his political future as he prepares to travel to France, Brazil, and Paraguay beginning Wednesday.

The CDP victories in the Shimane No. 1 district, the Nagasaki No. 3 district and the Tokyo No. 15 district reflect the public backlash over a political slush fund scandal that has roiled the LDP and resulted in polls showing record-low support rates for the prime minister.