The Russian opposition party of slain politician Boris Nemtsov is forming a coalition with Alexei Navalny’s Progress Party, the parties announced on Friday. RPR-Parnas and the Progress Party stand as the most influential opposition parties in Russia and will run joint campaigns in this year’s regional elections and next year’s parliamentary elections. They are joined by Democratic Choice, led by former Minister of Energy Vladimir Milov.

Together, the three parties hold only one seat in a regional legislature and no seats in the State Duma, which has been dominated by Vladimir Putin’s United Russia party since 2003. But for many Russian dissidents, they stand as the only true opposition voice in the country. Former Prime Minister and co-chairman of RPR-Parnas Mikhail Kasyanov said he hoped other opposition groups would join the coalition and run on their election lists. The alliance welcomes all “people of good will” to join the movement, according to the BBC.

Navalny, 38, founded the Progress Party in February  2014, but has been active in the Russian opposition movement for over a decade. The party failed to open enough regional offices in time to register for the 2016 State Duma elections, but now they will be able to run because Nemtsov’s RPR-Parnas party has a seat in a regional parliament, according to RT.

Navalny is a strong critic of Putin and a strong anti-corruption advocate who has repeatedly called Russia a fake democracy. He has twice been convicted of embezzlement related to his time as a governor’s aide in Kirov Oblast and an alleged fraudulent business transaction with a local political group in 2007. Navalny and his supporters maintain his innocence, calling the convictions politically motivated and orchestrated by the Kremlin. He has recently taken up vocally criticizing Putin for Russia’s alleged involvement in Ukraine.

Nemtsov, who was deputy prime minister for a brief time under Boris Yeltsin, was gunned down on a bridge near the Kremlin on Feb. 27. Many feared his death would silence the opposition movement, but thousands came out to pay their respects and rally in support of Nemtsov’s strong anti-Putin stance. Putin critics suggest the Russian president was somehow involved, but police have only arrested a handful of Chechens with close ties to Chechen President Ramzan Kadyrov. The prime suispect, Khamat Bakhayev, is being tried for murder, but strongly denies any involvement and says he was intimidated into confessing to the murder.