Russia’s Supreme Court upheld Monday a ruling barring liberal politician Boris Nadezhdin from running in the upcoming presidential election.

Nadezhdin, a city council member in the town of Dolgoprudny near Moscow, was nominated by the Civic Initiative party to run in an election President Vladimir Putin is all but set to win. He has been vocal against the war in Ukraine, garnering support among opposition-minded Russians.

In a statement on social media, Nadezhdin said he would continue to appeal his case. “We’re now writing a complaint to the presidium of the Supreme Court. From there we’re only one step away from the Constitutional Court,” he wrote. “For now, we are guided by Russian law.”

Nadezhdin's backer, the Civic Initiative party, doesn’t have representatives in the parliament. Russian election law requires such candidates to attain at least 100,000 signatures to qualify to run for the presidency. Nadezhdin secured 105,000 signatures after his call for a halt to Moscow’s invasion of Ukraine became a key part of his campaign.

However, on Feb. 21, Russia’s Central Election Commission declared more than 9,000 of the signatures submitted by Nadezhdin’s campaign invalid — enough to disqualify him from the race. In Russia, potential candidates can have no more than 5% of their submitted signatures invalidated.

So far, four candidates have been approved to contest in the March 15-17 election, including Putin. The other three are nominated by Kremlin-friendly parties represented in parliament and viewed by many as token contenders.