Oleg Shein, a candidate in the March 4 election in the city of Astrakhan, wrote on his blog that "the hunger strike has been stopped as the last of our comrades arrested by police was released."
Official results show Shein finished second in an mayoral election that was won by a candidate from President-elect Vladimir Putin's ruling United Russia party.
Shein and his supporters launched a hunger strike on March 16 against what they called vote-count irregularities.
Dozens of his supporters were arrested at various protest actions in Astrakhan and other cities.
Putin earlier this month asked why Shein was on a hunger strike instead of challenging the official results in court, prompting lawmakers from Shein's A Just Russia party to walk out of parliament.