Memo to the Democrats: Figure out how far Donald Trump is willing to travel on the ground before he gets bored and restless. Whatever the number is for our short-attention-span president (maybe a mile by golf cart and 10 miles by limousine), the Democrats should agree to build a border wall of precisely that length.

Consider it a Potemkin Wall.

The president, wearing a red MAGA cap, will smile broadly as he cruises along his 30-foot-high, transparent, solar-powered, fortified border barrier. And after about 10 minutes, Trump will veer off, convinced that the phantom wall extends from Texas to California.

In exchange for maybe five miles of this stage-set creation, Chuck Schumer and Nancy Pelosi probably could get anything from Trump. Amnesty for the Dreamers and their parents? Easy. Medicare for all? Done. Mike Pence to address a Planned Parenthood fundraising dinner? Even that’s possible.

OK, I’m overdramatizing the September accord between the erratic president and his erstwhile foes. But there appears to be a dollop of truth embedded in Schumer’s hot-mic moment when he was overheard Thursday saying about Trump on the Senate floor, “He likes us. He likes me, anyway.”

Others have pointed out that Hillary Clinton’s first year in the White House would have been judged a success if she successfully protected Obamacare from a Republican Congress and won statutory protection for immigrants illegally brought to America as children.

While Republicans such as Louisiana Sen. Bill Cassidy are mounting a final assault against Obamacare, and the protections for the Dreamers are far from codified into law, it certainly appears that the Democrats will have fared far better in Congress in 2017 than they could have imagined.

Trump as president may have no guiding ideology beyond pandering to the roar of the crowds at rallies and favoring those who praise him in private settings. But these personal calculations do not mean that Trump deserves praise for his intermittent September lurches toward the center.

Right or left

To put it bluntly, Trump would remain a reprehensible president even if he were to permanently move from the nationalistic right to the progressive left.

The case against Trump’s presidency is predicated on his uncontrollable mendacity; his disrespect for the highest office in the land; his willful ignorance about policy; his vicious personal attacks; his hot-tempered tweets about foreign policy; his contempt for ethics in government; and the way that he and his family have used the White House as a profit-making opportunity.

These same arguments would be valid if Trump — a man with no strong prior partisan allegiances — had bamboozled Democratic primary voters in 2016 and walked off with the nomination in Philadelphia. Had fate played out that way, I devoutly hope that I would have displayed the same moral courage as “Never Trump” conservative pundits who recognized that fitness for office always trumps party labels and campaign promises read off a teleprompter.

According to news reports, Trump is reveling in the positive TV clips that have flowed from his outreach to the Democratic congressional leadership. Some of this may reflect an inherent media bias in favor of bipartisanship and problem-solving. But it also suggests a psychological relief that — at least for the moment — Trump has stepped off the window ledge and has begun behaving like a vaguely normal president.

You could imagine virtually any president in the last 60 years talking about congressional gridlock like Trump did Thursday: “We have to get things passed. And if we can’t get things passed then we have to go a different route. We have to get things passed.”

Lonely at the top

It remains questionable how long Trump can last as a president without a party. Trump may not regard Mitch McConnell and Paul Ryan as boon companions. But the GOP leadership comes equipped with a weapon that any president should fear — the investigative powers of Congress.

Aside from a few high-profile hearings featuring ousted FBI Director James Comey, the GOP Congress has not scrutinized the Trump administration with a fraction of the zeal that they devoted to such Obama-era frenzies as Benghazi and Lois Lerner’s stormy tenure at the IRS.

But that could change in an instant if congressional Republicans become convinced that Trump is more comfortable trying to govern as an ersatz Democrat. Even if Congress, for the most part, leaves the Russian front to special counsel Robert Mueller, the Trump administration offers a tempting array of targets that could be transformed into must-watch television dramas.

Who wouldn’t enjoy an all-day hearing featuring Treasury Secretary Steven Mnuchin struggling to justify his request for a $25,000-an-hour Air Force jet as transportation for his European honeymoon? Equally fun would be watching Mnuchin explain the weird coincidence that he chose to visit Fort Knox with his new wife on a day when Kentucky was a prime viewing spot for the eclipse.

As a member of the White House staff, Ivanka Trump could not — in normal circumstances — be compelled to testify before Congress.

But it might be instructive for a congressional hearing to focus on the difficulties that most American fashion companies face in obtaining Chinese trademarks. Curiously, though, the company that Ivanka still owns has been particularly successful on the Chinese trademark front ever since her father became president.

The truth is that there is no safe harbor for Donald Trump. He chose to pursue the presidency out of arrogance despite his disinterest in the substance of the job. No amount of triangulation with the Democrats can save him from the long-term consequences of that uncontrollable egoism.

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and The Washington Post. Follow him on Twitter @MrWalterShapiro.