Trump is just tweaking his opposition. The more they are foaming at the mouth moonbats at election time the better this will go for him.
That was true early in his term where something like this would have the talking heads at CNN and MSNBC shaking their heads and delivering thoughtful blather on whether Trump really thought he could extend his term. Now his opponents just mock him for things like this. Trolling is only useful when it works and things like this aren't working anymore.