It seems that Donald Trump has made a rookie mistake on the economy.

While US presidents don’t always have control over business cycles, there is one hard and fast rule: Don’t stimulate the economy too early, because economic growth is likely to fade right at the time you are seeking re-election.

Trump appeared so excited — and maybe surprised — to get elected that he went all out with a tax reform policy that boosted the economy during his second year in office.

The economy now seems to be weakening despite the government’s largesse to taxpayers. And there is widespread talk of a recession right about the time Trump will be seeking re-election.

JPMorgan now predicts there is a 70 percent chance of a recession in two years, which — if the calendar I bought in the dollar store is correct — would be just in time for the 2020 election.

My prediction: There won’t be a recession in 2020, but the economy isn’t going to be roaring ahead either. And a slowdown in economic growth could be just as dangerous for the sitting president as a recession, which is defined by economists as two successive three-month periods in which the nation’s gross domestic product declines.