They will keep it up the full 8 years he is in office. Best they do it and look like the kooks they are. Waste their strength doing that. The kookier they look, even the Democrat Trump voters that really wanted to vote Bernie will stick with Trump.
The economy is starting to show some signs of life, so its likely there will be a second term. Remember, if the economy seems better, Trump wins.
To be honest, that will earn him my vote the second time, and be happy about it this time.