A former TV journalist who announced he would challenge President Putin in Russia's spring election has been banned from running.
Independent politician Yekaterina Duntsova wanted to run on a platform to end the war with Ukraine.
But the Election Commission voted unanimously to reject his candidacy three days later, citing 100 “errors” in his application.
Ms Dantsova said she would appeal the decision to the Supreme Court.
The March 2024 presidential election will be Russia's first since President Putin launched his full-scale invasion of Ukraine nearly two years ago.
Putin's immediate slap down of a critic will be seen by some as proof that no dissent will be tolerated in the campaign.
The head of Russia's election commission, Ella Pamfilova, said Ms Duntsova would not be allowed to advance to the next stage of collecting signatures from thousands of supporters.
“You are a young woman, everything is ahead of you. Any minus can always be turned into a plus. Any experience is still an experience,” she told Duntzova, 40, after the decision.
The former TV journalist had announced his candidacy for the presidency in November. At the time, he told the Reuters news agency: “Any sane person who takes this step would be afraid – but fear should not win.”
Russia's constitution was revised in 2020, raising presidential terms from four to six years and giving Mr Putin a clean slate to run for re-election by canceling his previous terms.
Moscow has sidelined opposition figures for years, with President Putin expected to win in March; The Kremlin says he enjoys genuine support among Russians.
Ms Dantsova has been vocal about her plans to launch a campaign to end the war in Ukraine and free political prisoners.
He responded immediately after the commission's decision. “We will appeal to the Supreme Court as this decision is not based on law,” said a message on his Telegram channel.
The commission said that 29 people have filed petitions to contest the presidential election so far. But after today's decision, Mr Putin remains the only candidate who can register as a candidate.
In November, a nationalist pro-war blogger who has been a vocal critic of Russia's military strategy in Ukraine said he wanted to challenge Putin and disrupt the “bad” referendum.
Igor Girkin, 52, was detained in July following social media posts critical of the president. He is now in jail on terrorism charges, which he denies.
Mr Putin recently showed a rare example of popular pressure – by cutting the cost of buying chickens and eggs. In a public phone-in, a caller berated the Russian president for the high price he had to pay.
With the election just three months away, President Putin has decided to exempt eggs and chicken from all import duties.