There will be at a minimum 10-15 contenders looking to run. They figure why not, a garden slug with halitosis and a bad attitude could beat Trump. Should be easy, they think.
Where they will go wrong is that they will A) continue thinking that flyover country is still peopled with ignorant gap-toothed rednecks, B) that Trump voters will be disheartened and will stay away from the polls, and C) despite the experience of the last election, they will still believe the cheerleaders of the MSM who will begin the victory party well before the polls close.
They will continue to beat the Democrat drum of identity politics, try and trot out the Mueller investigation, and recycle the same tired old "Russia Collusion" BS they've been touting for the last three years without any actual solid evidence linking any Russians to Trump. If it was there, don't ya think he'd have found it by now?