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Announcing his share purchase, Jack Dorsey tweeted that he was “investing in Twitter’s future.”Credit Dan Monick/Corbis Outline

Twitter has had a tough year. It has been slow to attract more users and has been battered on the public markets.

Now executives at the highest levels of Twitter are trying to show that despite it all, they still believe in the company.

Jack Dorsey, co-founder and interim chief executive, bought more than 31,000 shares of Twitter stock on Monday, amounting to roughly $875,000.

“Investing in Twitter’s future,” Mr. Dorsey wrote in a tweet on Monday that included a link to the Securities and Exchange Commission filing disclosing his purchase.

For Mr. Dorsey, who owns nearly 22 million shares of Twitter stock, it was a small addition to his holdings. And it came at a relatively low price; shares of Twitter have fallen by nearly a third over the last year.

The price of a Twitter share jumped 9 percent Monday, to $29.50.

The purchase is also a statement by Mr. Dorsey who, along with stepping in as the interim chief, has privately expressed considerable interest in becoming Twitter’s permanent leader, according to people familiar with his thinking who asked not to be identified because the conversations were private.

The company has yet to name a permanent chief executive, and Mr. Dorsey has not said whether he would take the position were it offered to him. But any decision would come at a tricky time for Mr. Dorsey, whose other company, Square, is preparing an initial public offering.

Twitter’s board has indicated that it wants its next chief executive to be at the company full time, putting pressure on Mr. Dorsey to decide between the tech companies he co-founded. That is, assuming he would be the board’s choice to run Twitter.

“I think for another company, spending months on end to find the right C.E.O. is appropriate,” said Brian Blau, an Internet analyst with Gartner. “I’m not sure Twitter has that luxury, or that they should have even gone forward without a permanent C.E.O. already on board.”

There also could be a shuffling of Twitter’s top ranks, according to people close to the company who requested anonymity because the board conversations were confidential. The shift would distribute power among Mr. Dorsey, Adam Bain, the company’s top advertising executive, and Evan Williams, a founder and board member of Twitter.