Mark Sanford speaks in Central Park in New York in July 2018. (Evan Agostini/Evan Agostini/Invision/AP)
Opinion writer

No one like President Trump had won before, so we assumed that no one ever would. We assumed that Republicans would always defend free trade, fiscal sobriety and international human rights, because in recent years they did. Decades before the civil rights era, when Democrats dominated in the South, no one could have imagined a solid Republican South. Before the world wars, did anyone imagine that the federal government would be so big, that people would become so geographically mobile, that African Americans would leave the South in such large numbers and that women would routinely work outside the home?

We humans suffer from a lack of imagination, a failure to conceive how dramatic events can scramble ingrained patterns. Every once in a while, it pays to check our assumptions.

We have assumed that Republicans would never abandon Trump, because they haven’t done so yet. But what if (not predicting, just hypothesizing here) the inverted yield curve does signal a recession, brought on in part by Trump’s trade war; if Trump’s disapproval rating doesn’t hold at 56 percent (as it is in the Fox News poll released on Wednesday) but climbs to 60 percent (i.e. the shootings in El Paso and Dayton, as Hurricane Katrina was for President George W. Bush, become the final straw for a chunk of the electorate); polls show multiple Democrats beating Trump by percentages outside the margin of error; former White House counsel Donald McGahn testifies as to multiple instances in which Trump obstructed justice; and one of the many Trump-made foreign policy crises spins out of control? One of those things surely could happen. It is not inconceivable that several of these could.

If things start going badly, the pace of Republican retirements will quicken, and the odds of a Democratic Senate majority will increase. At that point, some Republicans might figure that they can stick by Trump and watch both houses of Congress and the White House go Democratic, or they can find someone else to lead the party. Doubt arises as to their willingness to go down with the sinking Trump ship.

The point of the exercise is to underscore how weak is the assumption of absolute continuity. And that’s a pretty good reason for someone like former South Carolina governor and congressman Mark Sanford to start testing the waters for a primary challenge.

He is spending 30 days considering a possible presidential run. ″For all the credits and plusses the president may have, he’s got serious demerits with regard to tone,” Sanford said in a recent interview in New Hampshire. “And you cannot play the role of schoolyard bully and expect people to follow you. Leadership fundamentally at times is not about division and how we find contrast points, but it’s about inclusion and finding ways to work together.” On the policy side, Sanford blasts the president for recklessly running up the debt. “One of the cornerstones to the Republican Party historically was, do we spend beyond our means? Do we believe in some level of financial sanity? And that seems to have gone out of the window of late,” he asserted.

Sanford wouldn’t be called out as a liberal wolf in sheep’s clothing, as former Massachusetts governor Bill Weld (who is pro-choice, pro-gay rights and pro-environment) would. And like Sen. Eugene McCarthy (D-Minn.), who received more than 40 percent of the vote in the New Hampshire primary against Lyndon Johnson in 1968, or Pat Buchanan, who got 38 percent in his race in New Hampshire in 1992, Sanford wouldn’t have to win to highlight how weak a candidate Trump would be. He would simply need to be competitive.

And if by next year the economy is going sideways, multiple Democrats are beating Trump handily in the polls, McGahn has spilled the beans and a foreign crisis or two has overwhelmed Trump, leading to a further drop in his approval rating and a spike in the percentage of voters who definitely won’t vote for him, might Sanford or other Republican candidates who scrambled into the ring look like a better bet? Even if the White House might still be lost, Trump wouldn’t be around to drag the whole party under.

As I said, this surely is not a prediction. I’m not confident that any of the factors above will pan out. But by the same token, we should be open to the real possibility that the status quo won’t hold indefinitely. Things stay the same — until they don’t.

Read more:

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Elizabeth Bruenig: Evangelicals view Trump as their protector. Will they stand by him in 2020?

Jennifer Rubin: Democrats need to say what they’d do about all these crises