Dems say Mattis's departure is 'scary' and 'bad news'

News of Defense Secretary James MattisJames Norman MattisPentagon watchdog clears acting Defense chief in ethics probe New 2020 candidate Moulton on hypothetical Mars invasion: 'I would not build a wall' Trump learns to love acting officials MORE's departure from the Trump administration was met with bipartisan shock and concern on Thursday.

Mattis announced he would resign at the end of February, writing in his resignation letter to President Trump that he deserved a secretary "whose views are better aligned with yours."

Sen. Amy KlobucharAmy Jean KlobucharHarris wins town hall war among CNN viewers Cory Booker releases 10 years of tax returns Dems accuse White House of caving to Trump's 'ego' on Russian meddling MORE (D-Minn.) tweeted that she has "a lot of respect for General Mattis and after what happened yesterday the resignation is sadly understandable," referring to Trump's decision to withdraw U.S. troops from Syria.

House Minority Leader Nancy PelosiNancy Patricia D'Alesandro PelosiDemocrats are playing voters on their fantasies for impeachment The Hill's Morning Report - Trump tells House investigators 'no' Seven big decisions facing Biden in 2020 primary MORE (D-Calif.) told reporters: "I’m sad. I’m shaken by it. I had so much respect for him,” according to CNN's Manu Raju.

Sen. Mark WarnerMark Robert WarnerDems reject Barr's offer to view Mueller report with fewer redactions GOP senators divided on Trump trade pushback Hillicon Valley: Trump unveils initiatives to boost 5G | What to know about the Assange case | Pelosi warns tech of 'new era' in regulation | Dem eyes online hate speech bill MORE (D-Va.), vice chairman of the Senate Intelligence Committee, suggested the Trump administration would be destabilized by the Defense secretary's departure.

"This is scary. Secretary Mattis has been an island of stability amidst the chaos of the Trump administration," he wrote on Twitter. "As we’ve seen with the President’s haphazard approach to Syria, our national defense is too important to be subjected to the President’s erratic whims."

Rep. David CicillineDavid Nicola CicillineFacebook expects B-B fine over Cambridge Analytica Bipartisan lawmakers urge Trump to reconsider Central America aid cuts Dems charge ahead on immigration MORE (D-R.I.) called the resignation a “dire omen.”

“James Mattis was the last adult left in the room,” he tweeted. “He was maybe the last person who could tell this President 'No.' His departure is a dire omen for the future of our alliances and the security of our country.”

Mattis, a former general, was confirmed for the top Pentagon post in a 98-1 vote in the Senate; the sole dissenter was Sen. Kirsten Gillibrand (D-N.Y.).

Sen. Chris MurphyChristopher (Chris) Scott MurphyOnly four Dem senators have endorsed 2020 candidates More than 30 Senate Dems ask Trump to reconsider Central American aid cuts Long-shot goal of nixing Electoral College picks up steam MORE (D-Conn.) called Thursday's news “devastating.”

“Just imagine the morale crisis at the Department of Defense right now, having sustained the 1-2 punch of the Syria reversal and Mattis resignation,” he tweeted. “Devastating.”

High-profile Republicans also expressed concern over the resignation.

Sen. Lindsey GrahamLindsey Olin GrahamBarr to testify before Senate panel next week on Mueller report Kushner saying immigration plan will be 'neutral' on legal admissions: report Africa's women can change a continent: Will Ivanka give them her full support? MORE (R-S.C.) said the news filled him with "great sadness."

"It is with great sadness that I was informed of the resignation of General Mattis," he wrote. "He is one of the great military leaders in American history. He should be proud of the service he has rendered to President @realDonaldTrump and our nation."

Sen. Ben SasseBenjamin (Ben) Eric SasseAfrica's women can change a continent: Will Ivanka give them her full support? Senate needs to stand up to Trump's Nixonian view of the Fed GOP senators divided on Trump trade pushback MORE (R-Neb.) said Mattis was important for curbing Trump’s isolationist tendencies.

“This is a sad day,” Sasse tweeted. "General Mattis was giving advice POTUS needs to hear. Mattis rightly believes that Russia & China are adversaries, and that we are at war with jihadists across the globe who plot to kill Americans. Isolationism is a weak strategy that will harm Americans...”

Sen. Marco RubioMarco Antonio RubioDems plot aggressive post-Mueller moves, beginning with McGahn Senate Republicans tested on Trump support after Mueller Cuban negotiator says Trump's efforts to destabilize Cuba's government will fail MORE (R-Fla.) said Mattis's resignation letter made it clear that America is headed for a "series of grave policy errors which will endanger our nation, damage our alliances & empower our adversaries."

"I hope we who have supported this administrations initiatives over the last two years can persuade the President to choose a different direction," Rubio added. "But we must also fulfill our constitutional duty to conduct oversight over the policies of the executive branch."