You aren’t going to see many MAGA caps among under-30 Americans. Photo: Drew Angerer/Getty Images

It’s not exactly breaking news that millennials are not a hotbed of support for Donald J. Trump (or for that matter, his party). But via Axios, we learn that the latest weekly Gallup approval-rating numbers for the president among 18-to-29-year-olds have hit a dismal new low of 20 percent.

Trump’s approval rating in this age cohort has been sloping downward since late April, when it stood at a merely abysmal 36 percent.

Like most Republicans, of course, Trump’s popularity is directly proportional to the number of years poll respondents have been walking the earth. He’s currently at 33 percent among 30-to-49-year-olds; 42 percent among 50-to-64-year-olds; and 43 percent among those over the age of 65. If you have to pick where to be strong or weak, this is the pattern you’d like in the very short term, since likelihood to vote is also more or less directly related to age. These Gallup numbers are not screened for voter registration, much less likelihood to vote, so the overall profile for Trump isn’t quite as bad as it looks when it comes to people who will, for example, be voting in 2018.

In the long run, though, you don’t want your political party to be led by someone who is loathed by the voters of the future. No, people of a given generation don’t always vote the same way over time, but when there is a degree of antipathy this strong, it’s hard to overcome.