Though he strongly supported Józef Piłsudski during the May 1926 Coup, he later joined the center-left opposition. From 1928 to 1930 he was the third Marshal of the Sejm. When Piłsudski entered the Sejm chamber, accompanied by a sizable military escort, Daszyński refused to open the Sejm session. He ended his political career in 1930 when Piłsudski dissolved the Sejm.