Sen. Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.) on Thursday slammed “Wall Street Democrats” campaigning against his progressive goals while teasing a possible 2020 White House bid.

Sanders slammed think tank Third Way for running ads in early primary states that single him out, accusing the group of attempting to undermine his progressive goals.

In a fundraising email, Sanders asked for donations to "fight back" and send a message that "we will NOT let the political and financial elite of this country buy this election and scare candidates from supporting a progressive agenda."

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“They not only want to discourage or defeat a Sanders candidacy, they want to make sure that the progressive agenda is not advanced by anyone,” the letter reads.

Sanders accused groups like Third Way of wanting to return to a “failed corporate approach,” which he claimed led to increased income and wealth inequality.

“Our agenda terrifies the political and financial establishment of this country,” the letter reads.

In a statement to The Hill, a spokesperson for Third Way said Democrats should be concentrating their efforts on candidates with "the best chance of beating Trump," claiming that the 2018 midterm elections "proved conclusively" that Sanders "fail[ed] that test."

"By far the most important question that Democrats should be asking is which candidate and which set of ideas has the best chance of beating Trump. The midterms proved conclusively that the Sanders ideas fail that test," Matt Bennett told The Hill.

"It just is not what Democratic and Independent voters want," he continued. "So yes, it’s an honor to be included in his fundraising effort — he clearly sees us as an influential critic."

If Sanders were to launch a 2020 presidential bid, he'd likely enter a crowded primary field to challenge President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE. High-profile political figures, like former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE, Rep. Beto O'Rourke Beto O'RourkeJimmy Carter says his son smoked pot with Willie Nelson on White House roof O'Rourke endorses Kennedy for Senate: 'A champion for the values we're most proud of' 2020 Democrats do convention Zoom call MORE (D-Texas) and former New York City Mayor Michael Bloomberg have all been floated as possible contenders.

According to a new The Hill-HarrisX poll, Trump nearly ties with Sanders in a hypothetical 2020 matchup, with 37 percent saying they would vote for Trump, and 38 percent picking Sanders.

— Updated 5:45 p.m.