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

News of Defense Secretary James MattisJames Norman MattisTrump nominates ambassador to Turkey Overnight Defense: Trump declares border emergency | .6B in military construction funds to be used for wall | Trump believes Obama would have started war with North Korea | Pentagon delivers aid for Venezuelan migrants Top US general: Trump wrong on Syria pullout, ISIS defeat 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 KlobucharNewsom endorses Kamala Harris for president Pollster says current 2020 surveys like picking best picture Oscar before movies come out O’Rourke heading to Wisconsin amid 2020 speculation 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 PelosiConstitutional conservatives need to oppose the national emergency House Judiciary Dems seek answers over Trump's national emergency declaration Why don't we build a wall with Canada? 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 WarnerThe Hill's 12:30 Report — Presented by Kidney Care Partners — Lawmakers scramble as shutdown deadline nears Steel lobby's PR blitz can't paper over damaging effects of tariffs Drama hits Senate Intel panel’s Russia inquiry 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 CicillineForeign Affairs chairman: US military intervention in Venezuela 'not an option' Greedy tort bar tarts up the CREATES Act Whitaker takes grilling from House lawmakers 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 MurphyHouse passes bill to end US support for Saudi war in Yemen This week: Border deal remains elusive as shutdown looms Border talks stall as another shutdown looms 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 GrahamThe Memo: Trump and McCabe go to war Graham seeks new Rosenstein testimony after explosive McCabe interview Senate confirms Trump pick William Barr as new attorney general 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 SasseOvernight Health Care — Sponsored by America's 340B Hospitals — Push for cosponsors for new 'Medicare for all' bill | Court lets Dems defend ObamaCare | Flu season not as severe as last year, CDC says Senate approves border bill that prevents shutdown The Hill's 12:30 Report — Presented by Kidney Care Partners — Lawmakers scramble as shutdown deadline nears 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 RubioOn The Money: Trump declares emergency at border | Braces for legal fight | Move divides GOP | Trump signs border deal to avoid shutdown | Winners, losers from spending fight | US, China trade talks to resume next week Trump declares national emergency at border Democrats veer left as Trump cements hold on Republicans 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."