Julian Zelizer is a history and public affairs professor at Princeton University and the editor of " The Presidency of Barack Obama: A First Historical Assessment ." He's also the co-host of the "Politics & Polls" podcast. Follow him on Twitter: @julianzelizer . The opinions expressed in this commentary are his own.

(CNN) President Donald Trump is shaking things up once again. He is using his deep experience on "The Apprentice" to jettison some high-profile administration officials who are rubbing him the wrong way. Trump seems eager to orchestrate a purge -- he said this week that there "will always be change."

And a lot of change could be coming. CNN's Jim Acosta reported a source close to the White House saying, "Everyone loves a season finale."

This week, the first to go was Secretary of State Rex Tillerson . Although the timing is unclear, the next official facing possible replacement may be national security adviser H.R. McMaster , who like Tillerson, has never seemed to get along well with the commander in chief. As someone who has written a book about the failure of political and military leaders to be honest about Vietnam in the 1960s, McMaster didn't appear to be a particularly good fit for this White House.

The shake-up is the latest in a series of rapid-fire departures that have taken place over the past few weeks, including Gary Cohn (National Economic Council director), Hope Hicks (White House communications director), John McEntee (personal aide to the President) and Josh Raffel (White House communications aide).

And these come on top of a number of other high-profile exits such as Steve Bannon, Reince Priebus, Anthony Scaramucci, Sean Spicer and Michael Flynn that have made this White House feel like a game of musical chairs.

The possible removal of McMaster, the firing of Tillerson and the resignation of Cohn are perhaps the most problematic. By ousting three voices who have been the most at odds with the style of the President and key parts of his policy agenda, Trump is in the process of creating a dangerous echo chamber. His inner circle will be filled with people who sound just like him or who are willing to carry out whatever he says.

Rather than broadening the range of voices who have a place at the table and who can provide him with diverse analysis about how to handle the crises that the nation faces, Trump seems instead to be getting rid of anyone who sings even a slightly different tune.

With any president, such insular thinking is a problem. President Lyndon Johnson banished critics of the Vietnam War such as his vice president, Hubert Humphrey, from his inner council of advisers. This was also evident when President George W. Bush only heard "yes" men and women as he dragged the United States into the disastrous Iraq War.

In Trump's case, the problem could be even worse. This President is so lacking in experience and is so unstable it is triply urgent to have countervailing forces present at the table to help guide him through the rest of his presidency.

But there is no evidence that Trump recognizes this need, and these departures place the country in an enormously risky place. The United States has been lucky that we have not yet faced a major national security or economic crisis since 2017 that would require the President to figure his way through an explosive situation. The odds are this will happen at some point. During such moments as the Cuban Missile Crisis in 1962 or on 9/11, even the wisest president needs to hear all the options on the table and needs to hear from advisers who strongly disagree with him. The nation already got a taste for how things could go terribly wrong with Trump's failed response to violence in Charlottesville, Virginia, and the hurricane in Puerto Rico.

Some of the greatest moments in presidential history have taken place when our top leader is forced to contend with advisers who challenge their basic worldview. Secretary of State George Shultz pushed President Ronald Reagan away from his hawkish default position and toward seizing the opportunity that emerged when Soviet leader Mikhail Gorbachev showed interest in striking an arms deal. The hawks said Gorbachev was a tool of the Kremlin. Shultz and his allies said the possibility for change was real -- and they were right.

A president who lacks challenging voices in the Oval Office is also more likely to become downright Nixonian in responding to an investigation as serious as the one being conducted by Robert Mueller. The temptation for the President to take aggressive steps to stifle the process will only grow as he keeps finding fewer and fewer checks around him.

The dangers of Trump governing in an echo chamber are amplified by the state of Congress. Not only do we lack a condition of divided government that can check the President, but we have a Republican Congress fiercely loyal to its partisan cause and unwilling to push back against the President on almost anything. This was clear when the House Intelligence Committee dropped the entire investigation about Russia without any real justification.

McMaster's potential departure means that one more of a small handful of voices who don't see eye to eye with this President would be gone. Trump, already in a circular conversation with Fox News, will only be able to see one way out of any jam. The voices in the room that are not coming from the television set will probably sound exactly like his.

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The only possible solution at this point will come from Congress. Democrats can capitalize on the slim Republican majority in the Senate by blocking bad Cabinet nominations if they can pick off a handful of GOP votes.

If no Republicans in Congress will deal with the serious instability that we face with this President in office, the only viable alternative is for Democrats to gain control of the House and Senate in the 2018 midterms and take on this responsibility for themselves. The special election in Pennsylvania showed that the possibility of a Democratic wave is very real. In the meantime, the risks are grave.