When the two previous Republican candidates for President of the United States issue a public warning about their party's front-runner this year, it is time to take notice. No precedent in recent American history exists for the statement its 2012 nominee, Mitt Romney, made yesterday which was endorsed by 2008's John McCain. But then, no precedent exists for the success so far of Donald Trump, who has been neither a state governor nor a member of Congress.
He has no record of decision making outside of the business he inherited and has run as a personal fiefdom. According to the Economist, he has not led a publicly listed company with boards of directors and shareholders to hold him to account. He is accustomed to operating on his own instincts and giving orders to minions who must listen to him. It is not ideal preparation for the arts of persuasion and compromise that government requires.
Mr Trump seems to be profiting from a mood of impatience with political compromise, especially among Republican voters.
In an excellent essay we published last weekend, Robert Kagan of the Brookings Institution argued the Republican Party is reaping what it has sown with its extremism in Congress against President Obama's legislation and budgets, taking the federal government to the verge of shutdown at times. Mr Trump is talking like another "Tea Party" politician and the party's worry is that, unlike them, he will not hesitate at the precipice.
Mr Trump talks very tough about building up the US military to be the mightiest the world has seen (it already is) and of reinstating waterboarding torture "and worse" against suspected terrorists, and crushing Isis. The judgment and temperament he is exhibiting in the election are not those of anyone the world would like to see with his finger on the button, though to his credit, Mr Trump is a rare Republican who acknowledges the mistakes of the party's last tough-talking President who invaded Iraq unprovoked.
The world should be just as worried about the economic protectionism Mr Trump promotes. He promises to build a wall against Mexico and has no regard for the trade treaties previous Presidents have made. This, too, is standard election fare. Candidates routinely promise to review trade agreements and, once elected, come to terms with them. Mr Trump might not. He is a property tycoon, not an international trader. He is appealing to people who are easily persuaded their livelihoods and jobs are endangered by imports and immigration.
Mr Romney issued his warning yesterday in words Mr Trump's following would understand. Mr Trump was a "fraud", a "con artist", Mr Romney said. "He's playing the American public for suckers".
It is easy to dismiss these sentiments as the panic of the party "establishment" at the prospect of a rogue carrying its banner into the general election but it is more calculated than panic. Mr Romney declined to endorse any of the other remaining candidates, giving a boost to all three.
The only way Mr Trump may be stopped is if two or three of the others can take the nominating convention to a second ballot. Should that happen Mr Trump might run as an independent, splitting the Republican vote and handing the Presidency to the Democrats, probably Hillary Clinton.
It is a measure of their concern that responsible Republicans would run that risk.
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