President Trump's disgraceful behavior at Monday's summit with Russian President Vladimir Putin was astonishing. But it shouldn't surprise us.

The real question is what happens now.

In the face of overwhelming evidence that Russia meddled in the 2016 election to help Trump win, the American president sided unequivocally with Putin's denial of interference — and against Trump's own intelligence services. America's commander in chief even volunteered that "we're all to blame" for the increase in tensions between the two countries in recent years. About Russia's annexation of Crimea and launching of chemical weapons attacks on British soil Trump had nothing critical to say.

It's astonishing. But it is sadly unsurprising. This is exactly the kind of borderline treasonous behavior we have all come to expect from Trump. Whatever the reason — Russian kompromat, financial leverage over Trump's real estate empire by Russian oligarchs close to Putin, comparatively innocent admiration on the part of the American president for Putin's strongman style of autocratic rule — Donald Trump did exactly what his track record would lead us to expect him to do. He fawned over and defended Vladimir Putin — to the clear detriment of America's national interest and standing in the world.

On the campaign trail, Trump was consistently pro-Russia and pro-Putin, just as he was consistently dismissive and denigrating toward NATO and many of our democratic allies. Over the past week, Trump's insulting behavior toward key members of the Western alliance (including our closest ally, Great Britain), followed by his groveling, obsequious treatment of Putin are exactly the kind of actions one might have predicted two years ago.

It's incredible, but again, unsurprising. America has a president who thinks and acts in a way that almost perfectly inverts what one would expect from a president of either party.

The question now is: How do we get ourselves out of it?

This is where things get truly worrying.

The president's shocking and shameful performance is coming in for fairly intense criticism from Republican officeholders. In perhaps the most fiery statement, Sen. John McCain (R-Ariz.) called the Trump-Putin presser "one of the most disgraceful performances by an American president in memory. The damage inflicted by President Trump's naiveté, egotism, false equivalence, and sympathy for autocrats is difficult to calculate."

Strong words. But what will Republicans actually do beyond issuing sharply worded statements? Will any senators switch parties — or even vote against Trump? Will any House Republicans refuse to work with the administration? Will any congressional committees truly investigate any of this? Will they pass legislation protecting Special Counsel Robert Mueller? Will anyone on the president's national security team resign in protest?

Don't bet on it. Because however much those who occupy the top positions within the Republican Party may be disgusted by the president, Republican voters approve of him.

Trump's overall approval sits at roughly 42 percent, which is on the low side, but roughly five percentage points higher than where he was last summer, quite close to where President Obama was at this point in his presidency, and just four points below what it took for him to beat Hillary Clinton in 2016.

When it comes to members of his party, Trump is astonishingly popular. At 90 percent own-party approval, he is in fact one of the most popular Republican presidents in history. As long as that continues to be the case, Republicans in elective office will rant and rave, stomp and groan about his humiliations on the world stage. But then they will go back to governing in his name.

The sorry fact is that this is the properly democratic response. The GOP is a party. A party is supposed to be responsive to its voters. And this party's voters approve of the president.

Or at least they have up until now.

Trump is notorious for declaring in the midst of the 2016 Republican primary contest that he could shoot someone in the middle of Fifth Avenue and still receive the support of his voters. His wildly unorthodox (and stunningly successful) campaign amply demonstrated the veracity of the observation, at least in metaphorical terms. And this has continued to be the case throughout the tumult and ceaseless churn of his administration's first 18 months in office, even as his level of support within the party has risen.

From the beginning, critical observers and members of the Republican establishment have wondered: What, if anything, would be considered too much for his supporters? Are there any limits to their support? What would be sufficient to break his hold over their minds and political imaginations?

The events of July 16, 2018 will be an instructive test.

Was the president's performance the geopolitical equivalent of shooting someone in the middle of Fifth Avenue? Or was it something worse? And even if it was, will it be judged bad enough by the Republican rank-and-file to make a meaningful dent in his own-party support?

If not, nothing significant about our domestic political situation will change.

What will change is America's place and role in the world. And not at all in a good way.