State Department science envoy Daniel Kammen resigned Wednesday, citing President Donald Trump's "failure to condemn white supremacists and neo-Nazis."

"Your response to Charlottesville enables racism, sexism, and harms our country and planet."

—Daniel Kammen, UC BerkeleyBut his resignation letter was more than a critique of Trump's failure to adequately denounce white supremacist violence, which left one dead and many more injured in Charlottesville, Virginia. It also contained a rather unsubtle message, spelled out by the first letter of each paragraph: "IMPEACH."

Kammen, who is also a professor of energy at the University of California, Berkeley, posted the full resignation letter on Twitter:

Mr. President, I am resigning as Science Envoy. Your response to Charlottesville enables racism, sexism, & harms our country and planet. pic.twitter.com/eWzDc5Yw6t — Daniel M Kammen (@dan_kammen) August 23, 2017

While noting that Trump's defense of neo-Nazis was the final tipping point in his decision to resign from his State Department post, Kammen wrote that the president's Charlottesville remarks were "consistent with a broader pattern of behavior that enables sexism and racism, and disregards the welfare of all Americans, the global community, and the planet."

"Acts and words matter," Kammen added, addressing Trump directly. "To continue in my role under your administration would be inconsistent with the principles of the United States Oath of Allegiance to which I adhere."

Kammen's resignation—and his not-so-subtle parting shot at Trump—comes just days after members of the president's Committee on the Arts and Humanities resigned en masse, submitting a letter that contained an acrostic of their own: "RESIST."

"This president has proven time and time again that he doesn't have the maturity or the temperament to govern."

—Rep. Cedric RichmondAccording to recent polling data, a growing number of Americans stand with Kammen in his seeming desire for Trump to be impeached. A survey published by the Public Religion Research Institute last week found that 40 percent of Americans believe Trump should be impeached, a 10-point jump in a span of six months.

Previous polls have found support for impeachment as high as 48 percent.

Lawmakers have also increasingly begun to question Trump's fitness to serve as president.

"This country is having a crisis of leadership," Rep. Cedric Richmond (D-La.), chairman of the Congressional Black Caucus, said during a recent press call. "This president has proven time and time again that he doesn't have the maturity or the temperament to govern in a common-sense manner."