Following the “if you don’t have anything nice to say, don’t say anything” adage, Senate Foreign Relations Committee chairman Bob Corker (R-Tenn.) put out an effusive statement thanking outgoing national security adviser H.R. McMaster for his service: “General McMaster has served our nation incredibly well for 34 years, and I thank him for the work he has done in leading the National Security Council,” Corker wrote on Twitter. “It has been a privilege to work with him on some of the most pressing issues facing our country.”

He said nothing about John Bolton, who will replace McMaster.

Bolton, a frequent figure on Fox News and a prolific op-ed writer, is a fiery, controversial hawk and is prone to advancing positions few Republicans feel comfortable advocating. He still passionately supports the Iraq War, a conflict President Trump has often criticized. Bolton is an avid free-trader, while Trump is slapping tariffs on trading partners right and left. Bolton is a virulent anti-Putin advocate, seeing him (correctly) in the mode of aggressive expansionists and destabilizers. Trump, of course, has a weird aversion to criticizing Russian President Vladimir Putin or taking meaningful actions against Russia. Bolton is not strictly speaking a “neo-conservative,” as his concern for human rights is muted. (He is, for example, full of praise for Egyptian autocrat Abdel Fatah al-Sissi who is an ally against terrorists and Iran but has an atrocious human rights record.)

But — and here is what has left a great deal of the foreign policy community numb and anxious — Bolton frequently advocates use of military power, specifically against Iran and North Korea. With regard to North Korea, he believes diplomacy is useless and the only “solution” is reunification of the Korean Peninsula — as a free and democratic country. If that is a short-term goal rather than a long-term aspiration, a massive war almost certainly would be necessary. On Iran, he has declared the deal unfixable and advocated for military strikes on Iran.

The question of the moment is whether the John Bolton we read in print and see on TV will be the same John Bolton who is charged with coordinating foreign policy. Advocating in print a position a Democratic president will never undertake is one thing; presenting to your boss a viable plan for military action that may result in mass casualties is quite another. In other words, we’re about to find out if Bolton is really serious about all his views or has simply enjoyed the role of gadfly.

Richard Haass, head of the Council on Foreign Relations, tweeted a reminder that the national security adviser is supposed to be first and foremost an honest broker, formulating options for the president and trying to reconcile conflicting views before issues require the president to intervene. Haass tweeted that “the obvious question is whether John Bolton has the temperament and the judgment for the job.” Many on the Hill and in the foreign policy community think he doesn’t.

You may recall Bolton could not get sufficient votes in a GOP-controlled Senate to avoid filibuster of his nomination to the United Nations nor for a post at Foggy Bottom itself. He was instead given a recess appointment to the United Nations under President George W. Bush. The national security adviser is not a post requiring Senate confirmation.

Bolton’s appointment should have been no surprise given his frequent visits to the White House and rumors (batted down emphatically just a week ago by Sarah Huckabee Sanders) of McMaster’s departure. Nevertheless, numerous foreign policy gurus outside government and staffers on the Hill usually brimming with opinions were strangely muted, as if they cannot quite believe what has happened. One staffer wisecracked, “I am rocking back and forth in a corner for now.”

Ever-eager to praise Trump, Sen. Tom Cotton (R-Ark.) pronounced Bolton an “excellent” pick. After critics assimilated the news, the negative reviews began to pour in.

The ranking Democrat on the Senate Foreign Relations Committee, Robert Menendez (D-N.J.) feels quite differently. “While the president may see in Mr. Bolton a sympathetic sycophant, I would remind him that Mr. Bolton has a reckless approach to advancing the safety and security of Americans – far outside any political party,” Menendez said in a recent statement. “Let us recall that Mr. Bolton forcefully advocated for the Iraq war, which as of this week is in its 15th year. I proudly voted against the Iraq war, which has taken the lives of nearly 4,400 Americans, wounded over 32,000 more, and resulted in hundreds of thousands of Iraqi civilian deaths to date.” He vowed to “conduct vigorous oversight of our nation’s foreign policy during these chaotic times.”

Senate Minority Leader Charles E. Schumer (D-N.Y.) echoed that sentiment in his own statement. “Mr. Bolton’s tendency to try to solve every geopolitical problem with the American military first is a troubling one. I hope he will temper his instinct to commit the men and women of our armed forces to conflicts around the globe, when we need to be focused on building the middle class here at home.”

Jake Sullivan, Hillary Clinton’s senior foreign policy adviser during the campaign, was more blunt. “John Bolton is reckless, arrogant, trigger-happy, and he treats people shabbily, including the public servants who have worked for him.” Another moderate foreign policy voice said simply, “He is very hard line . . . . I don’t know if he will be OK. I do know I will miss HR [McMaster].”

A more nuanced view came from a former senior intelligence official. “Trump will now be surrounded by people with very similar views on key issues such as Bolton and [Mike] Pompeo. This can be a problem and can close off important options unless Bolton rises to the occasion as a national security advisor — whose principal job is always to tease out a range of views and present them fairly to the president and lay out the pros and cons of each option,” the official told me. “That is when the national security process has worked best under leaders like Brent Scowcroft and Bob Gates. Bolton is untested in that capacity and so much will ride on whether he has the temperament and ability to orchestrate such a process.”

A moderate foreign policy expert (who defended the surge in Iraq) said simply, “Yes, it’s a big change and to my mind not in a good direction.”

The Bolton pick should be a wake-up call to Republicans who always assumed wise, calm advisers would be there to constrain Trump. It should motivate both Republicans and Democrats to start reclaiming Congress’s power, for example, by declaring that congressional authorization is required for a first strike on either Iran or North Korea. They cannot prevent Bolton from assuming his job, but together with Republican colleagues can begin to exercise more restraint on the use of force and, as Menendez suggested, to conduct robust oversight.

As for outside foreign policy gurus who have advocated high-stakes strategies (e.g., threatening to pull out of the JCPOA and use military force against Iran), they would do well to realize this is no academic exercise. In Bolton, the president has someone who may well encourage his most outlandish ideas.