Billionaire Republican front-runner Donald Trump as president would be problematic for the US on many fronts. It presages multiple negative consequences at home and abroad that are mind-boggling.

Before a crowd of about 2,000 some days ago at the Georgia Congress Center, Atlanta, I witnessed Trump mesmerise the audience with a series of disjointed platitudes that defied any logic. Skipping from here and yonder, he brandished his narcissism, boasting of his business acumen and leadership skills. The hyperbolic diatribe went beyond the pale of decency. It was not comical.

Two men in their 30s extolled Trump’s ‘virtues’ of ridiculing the establishment and being a “strong leader“. They opined he was the only Republican candidate who could beat Hillary Clinton, characterised Senator Marco Rubio as a mere “teleprompter expert like Obama”, and Senator Ted Cruz as a “liar, not to be trusted”. They saw nothing wrong with Trump’s notion of erecting a wall along our border with Mexico. In their view, he won the argument with the Holy Father. They agreed with Trump’s declaration to repeal the agreement with Iran on nuclear weapons.

This was unfortunate in light of the pontiff’s efforts, in tandem with the Obama Administration’s, to foster ecumenical dialogue.

Media depiction of Trump as a “nationalist” and “populist” misses the essence of the man and the predicament he would cause the country. Unhelpful is the media’s penchant for sensationalism and dividends, combined with potential litigious concerns. This attitude frustrates candid reportage on Trump’s authoritarian character. Such flippancy only countenances his histrionics that resonate with those who harbour malevolent and atavistic thoughts, as well as a dangerous flirtation with autocracy.

Trump and his surrogates, for example Sarah Palin and Jerry Fallwell, as well as his blinkered followers, continue to reject Barack Obama as the legitimate president. Further, Trump’s allegation that Hillary Clinton “should go to jail — but the Democrats will protect her”, exemplifies the extent to which he would go to satisfy his overbearing ego.

It’s not hard to imagine how Trump’s temperament and bombast will sit with our friends and allies. It’s likely to irritate our partners and impede discourse over critical matters of mutual interest. While “national interests” are paramount in international affairs, there are mores and protocol in place to ensure civilised deliberations and interaction. Resorting to innuendos and threats will impede dialogue and decelerate momentum of ongoing efforts on behalf of the country. For example, intelligence-sharing with allies — critical to our fight against terrorism — requires mutual trust, competence, and a reliable disposition of the US President.

An “exceptional” US is not equivalent to being a “hegemon”, as pugnacious Trump seems to think. From our experience as US diplomats, my spouse and I know what public perception of hegemon means for our image abroad, our bilateral relations, and multilateral efforts, including on terrorism. His paltry specifics and unending forays against Republican opponents as well as President Obama mask a lack of understanding of the world. This do-it-myself attitude will not work. That’s a recipe for disaster.

As for our adversaries, Trump appears impatient and prone to resort to extreme methods without adequate consultations with the Legislative Branch. With regard to nominating Supreme Court justices, he seems predisposed to impose his preference based on strictly political criteria. His comportment and language project the impression of a propensity to rash moves that he would try to justify as pre-emptive in nature.

US democracy would be threatened were this mercurial candidate to occupy the Oval Office. The country can ill afford his legerdemain. Institutions are being threatened and early evidence of domestic instability is palpable. The two-party system would be put in question, again.

Under Trump, the Washington political gridlock would become an unforgettable nightmare. It could be destabilising for the US and the world.

Earle Scarlett is a former US diplomat with global experience. He resides in Atlanta. Send comments to the Observer or earlescarlett@gmail.com.