IN last Sunday’s column, I wrote about the dangers that a Hillary Clinton presidency poses for the country. Since this is the final week for Hillary skeptics to agonize over whether to cast a vote for Donald Trump, it seems appropriate to outline why the risks of Trump are so distinctive as to throw the perils of a Clinton presidency into relative eclipse.

This is a challenging thing to explain because Trump is, among recent American politicians, sui generis. The mistakes and blunders that an establishment liberal like Clinton is likely to make can be envisioned by looking at peers like Angela Merkel, at recent occupants of the White House, at Hillary’s own record. But there are no obvious analogues for a President Trump; all the comparables, from Arnold Schwarzenegger to Silvio Berlusconi, only reflect part of what we would get with the Republican nominee as a superpower’s president.

So considering the dangers of Trump requires a grounded speculation, which is what I’ll attempt here. These are not my worst-case scenarios: They do not involve Trump making baldly authoritarian moves or accidentally touching off nuclear war. Rather, they’re three baseline dangers for a Trump administration, three perils that we would very likely face.

The first is sustained market jitters, leading to an economic slump. Trump’s election alone would probably induce a Brexit-esque stock market dip, but the real problem would be what happened next. Instead of Theresa May’s steadiness inspiring a return to fundamentals, you would have the spectacle — and it will be a spectacle — of the same Trump team that drop-kicked its policy shop and barely organized a national campaign trying to staff up an administration. Even without his promised pivot to mercantilism and trade war, a White House run as a Trump production is likely to mainline anxiety into the economy, sidelining capital, discouraging hiring and shaving points off the G.D.P.