The half-life of most American’s political memory is two years at most. At four years, 3/4 will fondly remember Obunghole and look for a like kind encore. At eight years, 15/16 will remember him as the man who brought HOPE to the nation. And, at eight years you’ll have a whole new crop of young skulls full of mush thoroughly polluted by public schools and universities.
Look how fast Reagan faded from memory.
You are ignoring one other factor, in determining how future U.S. elections in ‘18 and in ‘20 goes: President Donald Trump’s winning, on the majority of issues. What Congress does before then should be kept separate from what President Trump does, before then. So far, President Trump is winning, and enough general election voters will pay attention to this.