MOSCOW — A young socialite and television journalist whose father was a close ally of Russia’s president, Vladimir V. Putin, declared her intention on Wednesday to challenge him in the presidential election scheduled for next March, a move liable to split the already feeble liberal opposition.

The journalist, Ksenia A. Sobchak, 35, announced her presidential run in a video online on YouTube and also published a letter in Vedomosti, Russia’s main business daily. She portrayed herself as a candidate for those who reject the status quo, a candidate who could give the struggling opposition a voice and challenge the tired, elderly candidates from established parties who have been around for decades.

“You want to show your active position, but your candidate is not authorized to run? You don’t have a candidate? Tick Sobchak,” she wrote in the newspaper. “You’re just using a legal and peaceful opportunity to say ‘Enough! I’m fed up with this!’”

The main liberal opposition candidate, Aleksei A. Navalny, has been banned from running because of convictions in fraud cases that he has called politically motivated.