"I think it's still a pillow fight" among the 20-something Democratic presidential hopefuls, said Bannon, who also formerly ran the Breitbart News far-right media outlet. "I don't see excitement in these candidates," which he said could open the nomination process to someone not in the race yet.
The Democratic Party's main objective is to beat Trump, said Bannon, adding that no candidate has emerged as being able to do so. He believes Trump will be reelected.
Bannon — who helped Trump win the White House in 2016 and influenced the early months of the administration — slammed former vice president and current Democratic front-runner Joe Biden.
"If the Democratic Party wants to take on Trump, I've got a news flash for them. They're not taking on Donald Trump with Joe Biden," Bannon contended. "Joe Biden's days of hitting a fastball are many years behind him."
A spokesperson for Biden was not immediately available for comment on Bannon's remarks.
Bannon said on "Squawk Box" that he sees the possibility of "people on the sideline" joining the race by this fall, positing Hillary Clinton or former New York City mayor and billionaire businessman Mike Bloomberg.
Both Clinton and Bloomberg have already said they are not running for president in 2020.
In June, Trump said in a "Meet the Press" interview on NBC that he would rather run against Biden than Clinton, saying she was a "ruthless and vicious" candidate during the 2016 race.