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

News of Defense Secretary James MattisJames Norman MattisThe Hill's Morning Report - Trump takes 2020 roadshow to New Mexico Trump needs a national security adviser who 'speaks softly' US could deploy 150 troops to Syria: report 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 KlobucharMSNBC Climate Change Forum draws 1.3M viewers in 8 pm timeslot The two most important mental health reforms the Trump administration should consider Sanders searches for answers amid Warren steamroller 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 PelosiBiden blasts Trump, demands he release transcript of call with foreign leader Pelosi wants to change law to allow a sitting president to be indicted Overnight Health Care — Presented by Partnership for America's Health Care Future — Walmart to stop selling e-cigarettes | Senators press FDA to pull most e-cigarettes immediately | House panel tees up e-cig hearing for next week 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 WarnerOvernight Defense: Trump hits Iranian central bank with sanctions | Trump meeting with Ukrainian leader at UN | Trump touts relationship with North Korea's Kim as 'best thing' for US Hillicon Valley: Zuckerberg courts critics on Capitol Hill | Amazon makes climate pledge | Senate panel approves 0M for state election security Zuckerberg woos Washington critics during visit 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 CicillineHillicon Valley: Lawmakers say Zuckerberg to 'cooperate' on antitrust probes | Dems see victory after McConnell backs election security funds | Twitter takes down fake pro-Saudi accounts Lawmakers say Zuckerberg has agreed to 'cooperate' with antitrust probe Judiciary Democrats press White House over antitrust probe of automakers 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 MurphyDemocrats hit Scalia over LGBTQ rights GOP signals unease with Barr's gun plan Trump administration floats background check proposal to Senate GOP 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 GrahamSenate Judiciary Committee requests consultation with admin on refugee admissions Trump reignites court fight with Ninth Circuit pick Trump judicial picks face rare GOP opposition 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 SasseManufacturing group leads coalition to urge Congress to reauthorize Ex-Im Bank The Hill's Morning Report - Trump ousts Bolton; GOP exhales after win in NC Trump endorses Sasse in 2020 race 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 RubioLiberal super PAC launches browser extension replacing 'Mitch McConnell' with 'Moscow Mitch' Trump faces difficult balancing act with reelection campaign Republicans wary of US action on Iran 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."