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WASHINGTON — President Donald Trump closed out one of his most prolific days on Twitter — 16 tweets in 24 hours — with a taunt aimed at North Korean leader Kim Jong Un Tuesday night.

Reacting to Kim's New Year's Day remarks in which he alluded to having a nuclear button at the ready, Trump asserted that his "Nuclear Button" is "much bigger & more powerful" than Kim's — "and my Button works!"

North Korean Leader Kim Jong Un just stated that the “Nuclear Button is on his desk at all times.” Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works! — Donald J. Trump (@realDonaldTrump) January 3, 2018

Public outcry was swift.

Republicans, like former chief White House ethics lawyer for President George W. Bush, Richard Painter, said the tweet was evidence of Trump's instability — and grounds for impeachment.

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This Tweet alone is grounds for removal from office under the 25th Amendment. This man should not have nukes. https://t.co/ymWija85o3 — Richard W. Painter (@RWPUSA) January 3, 2018

Painter lumped Trump together with the North Korean leader as "two psychologically unfit men crowing about their nukes ... Congress needs to deal with one of them and the U.N. Security Council needs to deal with the other."

Senate Minority Leader Chuck Schumer, D-N.Y., slammed Trump's "foreign policy by tweet" in remarks from the Senate floor Wednesday, while Democratic Congressman Eric Swalwell, D-Calif., invited his GOP colleagues to help check what he called "not normal behavior" from the president Tuesday night.

If you love our country, help me put this lunacy in check. Tell @realDonaldTrump this is not normal behavior. Any @HouseGOP members want to make sure Congress has some say before he pushes that button? https://t.co/qI7pVc3I5I — Rep. Eric Swalwell (@RepSwalwell) January 3, 2018

Former Vice President Joe Biden, speaking to reporters on Capitol Hill Wednesday, deemed the tweets "not presidential."

The Bulletin for Atomic Scientists — a group that informs the public about nuclear weapons risks — also sounded the alarm Tuesday night. Its editor-in-chief, John Mecklin, told Poynter Tuesday night Trump's tweets "increase the probability that North Korea will misinterpret normal military exercises as an attack" and respond accordingly.

"This could result in a back-and-forth series of military actions that might — actually, really — lead to worldwide thermonuclear war and the end of the human experiment," he said, adding that in his opinion, the president's tweets about North Korea constitute "an existential threat to humanity."

Some Twitter users pleaded with Twitter CEO Jack Dorsey to suspend Trump's account.

An activist group in San Francisco projected "@jack is #complicit" on the social media company's headquarters Tuesday night after the tweet was posted. Other users reported the tweet outright, receiving replies from Twitter that their report had been reviewed and the tweet was not in violation of rules about abusive behavior.

It's not the first time Twitter — Trump's preferred method of direct communication — has come under fire for playing host to the president's musings. When he threatened military action against Pyongyang last summer, users argued that his rhetoric violates Twitter's rules and terms of service barring threats of violence.

The rules tell users that "may not make specific threats of violence or wish for the serious physical harm, death, or disease of an individual or group of people. This includes, but is not limited to, threatening or promoting terrorism."