Donald Trump. Mark Wilson/Getty Images

The words "Trump" and "impeachment" are often seen in the same sentence now. Few think it would happen. But there's no question another presidential impeachment attempt would be a wrenching experience for the nation.

Geopolitics expert and Eurasia Group founder Ian Bremmer doesn't worry about impeachment. Speaking at the Mauldin Economics Strategic Investment Conference on Tuesday, Bremmer said he sees a different and more worrisome risk.

What If Trump's Generals Leave?

When Trump won the election, he knew that he lacked military and foreign policy experience. To that end, he brought in widely respected retired General James Mattis as secretary of defense and Lieutenant General Michael Flynn as his national security advisor.

Flynn didn't work out, obviously, but Trump replaced him with Lieutenant General H.R. McMaster.

Defense hawks breathed a sigh of relief with these appointments. At least someone with military sense would be at the table, they reasoned.

But would Trump listen to them?

Most accounts say yes. Mattis, in particular, has strong influence on military and foreign policy decisions. This proved invaluable as the Pentagon mounted attacks on Syria and geared up for a possible response to North Korean missile launches.

So, as long as the generals are there, Bremmer is confident Trump won't do anything crazy. But will they stick around? That is not at all clear.

Mattis or McMaster Could Resign Within a Year

Working for Donald Trump isn't easy. He vacillates, changes his mind, thinks out loud, and publicly blames subordinates when things go wrong. Not everyone can handle it, and plenty don't want to.

This may be one reason the administration has been slow to fill the hundreds of sub-cabinet positions that require Senate confirmation.

Last week, Trump sent McMaster to face the media in defense of disclosing sensitive information during his Oval Office meeting with Russian visitors. McMaster was clearly uncomfortable in the role. Many observers thought his answers misleading or worse. That's a tough accusation for a military man whose word has long been solid as a rock.

Bremmer's concern is that we will continue to see more incidents that are unpleasant for Mattis and McMaster. There may be others behind closed doors, too. At some point, one or both could decide he's had enough.

In that scenario, replacing them with equally respected figures might be difficult. So, then what? Who will get Trump's ear?

Bremmer doesn't know, but suspects the answer wouldn't be good. He sees a significant chance either Mattis, McMaster, or both will leave their posts within a year. This is a much higher probability than impeachment—and potentially far more dangerous.

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