Implying that special counsel Robert Mueller would somehow "overturn" Trump's election represented a new line of attack for the Trump campaign, which has so far mainly attacked Democrats, the media, and undocumented immigrants in its appeals for cash.

"We cannot let the swamp get away with using our government as a weapon to overturn elections and silence millions of American voters. Please make a contribution of $1 to help FIGHT BACK," said the email.

President Donald Trump's re-election campaign on Thursday sent out a fundraising email titled "Re: Russia," which suggested that donors could help the president fight special counsel Robert Mueller's investigation.

On the rare occasion that a Trump campaign email mentioned the Russia probe, it was only to label the probe a "witch hunt," or a "phony" narrative -- a far cry from the suggestion Thursday that Mueller could remove the president from office by overturning the results of the 2016 election, and essentially orchestrate a coup.

The more aggressive tone of Trump's latest fundraising email coincided with a similar shift that is reportedly underway among the president's legal team, towards a more combative approach to the Mueller probe.

On Thursday, John Dowd, Trump's personal attorney and his lead lawyer on the Russia inquiry, resigned. This was just days after Trump hired Joseph diGenova, a lawyer and cable news commentator who has repeatedly claimed that the special counsel's investigation is part of a vast government conspiracy against the president.

This idea that there are somehow two governments, one led by Trump, and another one plotting against Trump, was also evident in the Trump campaign email, which accused the Washington establishment of "using our government as a weapon" to overturn Trump's election.

House Minority Leader Nancy Pelosi, D-Calif., a perpetual boogey-man for the GOP, was singled out in the email and accused of, "using the Russia witch hunt as a political ploy to RAISE MONEY from her supporters." Which is, incidentally, the same thing that the Trump campaign was doing.

A Trump campaign spokesman did not immediately respond to an email from CNBC.