He displayed that characteristic on the first day of his presidency with false claims about inaugural crowds. Later, instead of accepting responsibility for the failure to repeal and replace Obamacare, the president blamed fellow Republicans such as Sens. John McCain and Mitch McConnell.
This past week, needing success on tax cuts to salvage a barren opening year, Trump submerged himself in needless controversy. That, too, was touched off by Trump's defensiveness over the solemn presidential task of consoling the families of fallen soldiers.
The cascading furor set the White House against a Democratic congresswoman in exchanges that tarnished the credibility of both Trump and White House Chief of Staff John Kelly. That it escalated into a direct confrontation with a gold star widow reflects the president's inability to let go.
"Trump is motivated by the same concern in all situations, which is to dominate and to be perceived as having won," Tony Schwartz, Trump's 1987 co-author on "The Art of the Deal," recently told The Washington Post.
That trait, combined with Trump's fleeting attention span and weak grasp of policy detail, fits poorly into a legislative process requiring teamwork.
Trump wants the biggest tax-cut in American history. But his initial claims that he could provide one without increasing the deficit proved so unrealistic that he scaled back his first outline.
He insisted his revised plan would help the middle class at the expense of wealthy taxpayers such as himself. But that appears so at odds with reality that Republican lawmakers are scrambling to revise it again.
Trump was reportedly surprised to discover some middle-class taxpayers would be hurt by losing federal deductions for state and local taxes, so elimination of that tax break is under review. When lawmakers considered compensating for lost revenue by taxing contributions to 401(k) savings accounts, the president summarily ruled that out via tweet.
Those changes, and the White House decision to jettison the House GOP "border adjustment tax," mean the tax cut will add that much more to federal deficits and debt. Unless other revenue raisers are found or Trump's "big, beautiful" tax cut is reduced, senators such as Corker and anti-deficit House conservatives find it tougher to vote yes.
The latest attack on Corker poses another danger. The Tennessee senator answered Trump by voicing concerns that other Republicans only whisper privately: that Trump is not only dishonest, but possibly unstable and dangerous as America's commander-in-chief.
Corker, the Senate Foreign Relations Committee chairman, wouldn't express confidence in Trump's command of the nuclear arsenal or say whether the president should be removed from office. If other Republicans see their legislative agenda as doomed anyway, they may feel emboldened to echo him.