Senator Elizabeth Elizabeth Warren has found a favourite set of adversaries in the 2020 presidential race - America’s billionaires.

In a new TV ad, the Democratic presidential candidate singles out a series of billionaires who have criticised her, showing footage of them and repeating her call for a wealth tax on the fortunes of the richest Americans.

Set to air on CNBC, it is the latest volley in the back-and-forth between Ms Warren and the country’s billionaires — or at least an outspoken handful of them who have criticised her candidacy publicly. It comes as Michael Bloomberg, the billionaire and former New York City mayor, is preparing to enter the presidential race.

“It is time for a wealth tax in America,” Ms Warren says in the ad, which shows her speaking at a recent town hall. “I’ve heard that there are some billionaires who don’t support this plan.”

Then it gets specific, identifying four of them and helpfully informing viewers of their estimated net worth. First is the hedge fund manager Leon G Cooperman, net worth $3.2bn (£2.5bn), who has publicly sparred with Ms Warren.

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“The vilification of billionaires makes no sense to me,” he is shown saying in the ad. “It’s bull.”

Then this flashes onscreen: “Charged with insider trading.” (The Securities and Exchange Commission sued Mr Cooperman and his firm, Omega Advisors, in 2016; he and the firm settled in 2017.)

The ad also shows footage of Joe Ricketts, founder of TD Ameritrade; Lloyd Blankfein, former chief executive of Goldman Sachs; and venture capitalist Peter Thiel.

The ad closes with Ms Warren asking the richest Americans to “pitch in two cents,” along with a list of social programmes that could be funded with the revenue from her proposed wealth tax.

Ms Warren wants to impose an annual tax of 2 per cent on net worth above $50m (£39m), and 6 per cent above $1bn (£780m). She would use the revenue from that tax to fund proposals like universal child care, free public college and student debt cancellation, as well as to help pay for “Medicare for all.”

In the primary race, Ms Warren generally has avoided taking shots at her Democratic rivals, but she has embraced the fight with her billionaire critics.

Last week, her campaign rolled out an online calculator showing what a billionaire would owe under her wealth tax, depending on the size of their fortune.

The calculator includes a link to show what Mr Cooperman, specifically, would owe under the wealth tax.

Mr Cooperman fired back Wednesday after Ms Warren’s new ad was reported by CNBC, calling her “disgraceful” in an interview with the cable network.

“In my opinion, she represents the worst in politicians as she’s trying to demonise wealthy people, because there are more poor people than wealthy people,” Mr Cooperman said.