If you’re an ambitious Republican, it’s time to start thinking about challenging Donald Trump for the GOP presidential nomination in 2020. If you don’t get going now, you’re doomed to be too late. Unless you’re a celebrity with hundreds of millions of dollars at your disposal, you’ll need to lay the groundwork for your campaign very, very early. Raising the necessary funds will mean assembling the right team, and that will take a lot of wheedling. I say start wheedling now. If you fear embarrassment, by all means be discreet about your intentions. While one can imagine there being a 2020 primary challenger who’s been vociferously opposed to Trump from the get-go, there could also be a candidate who runs against Trump more in sorrow than in anger—say a former Trump loyalist who wants to do right by the president’s base or an earnest conservative who gave Trump the benefit of the doubt for as long as she could before reaching the breaking point.

Why is now the right time? It wasn’t so long ago that Donald Trump would routinely crow about how well he was doing in the polls. As recently as February, the president declared that “any negative polls are fake news.” But the crowing has mostly stopped, presumably because even Trump realizes that he is profoundly unpopular. As Jonathan Swan of Axios reports, “Sources both inside and close to the White House are worrying about a loss of energy among the president’s base.” The most recent Gallup survey finds Trump’s approval rating at 36 percent, and there are signs that even the president’s most devoted supporters are losing faith.