"We need an exemplary business, financial, and global leader to manage through what is likely to be a critically important decade for our country in determining our destiny," Ackman said on Twitter Wednesday.

"Jamie Dimon is that leader," added Ackman, who runs a hedge fund called Pershing Square and made his name as an activist investor.

The endorsement comes after Dimon admitted in an interview with Bloomberg early Wednesday that the thought of running for public office had crossed his mind even though he is "quite happy" running the country's largest bank.