CNBC's Jim Cramer said Tuesday that Sen. Elizabeth Warren missed her chance to court ultra-wealthy voters who may have naturally supported her 2020 presidential run.

"She's scared people, and that's why I think people are flocking to other candidates," Cramer said, referring to Warren's bank-bashing and wealth-taxing proposals.

The Massachusetts Democrat, who has recently been sliding in the polls, currently trails former Vice President Joe Biden and Sen. Bernie Sanders, according to the latest RealClear Politics national polling average. At the height of her popularity, Warren was in second.

The fall in the polls coincided with Warren's heightened attacks on billionaires, Cramer pointed out. "Has she driven off billionaires who would've sided with her otherwise?" he asked rhetorically. "Has she alienated a group of people who would've been natural supporters?" A spokeswoman for Warren did not immediately respond to a request for comment.

Cramer's remarks come after a report that some of the wealthiest in Silicon Valley have hosted fundraisers for South Bend, Indiana, Mayor Pete Buttigieg, who is rising in 2020 Democratic presidential polls. On "Squawk on the Street" on Tuesday, he pointed to Warren's wealth tax proposals on billionaires, who think the measure goes too far and won't be successful.

Warren's plan calls for a 2% tax on families' net worth of more than $50 million, which she has turned into a rallying cry for the rich to pitch in 2 cents for every dollar above that threshold. Warren wants to put a 6% tax on household net worth over $1 billion.

In addition to opposing some of her proposed policies, Cramer said Monday on "Mad Money" that his conversations with Wall Streeters have turned up dissatisfaction with how she treated former Wells Fargo CEO Tim Sloan and billionaire Leon Cooperman. "When she decided to go after … charitable billionaires, I think people thought, "I'm not immunized one bit. I tried to do right thing and I still get attacked,'" he said.

Cramer has often said that he's tried to assuage Wall Street concerns about the liberal Warren. "The fear of Sen. Warren is getting overblown," he said in October, three weeks after saying financial industry CEOs and other corporate leaders were telling him that "she's got to be stopped."