The fact of the matter is that President Trump won the election with sufficient votes over the Democratic candidate. That means a good portion of this country (a majority of the voting population....or more precisely, the electoral college....) supported him then....and to a large degree still does. That's just fact, not opinion.
There may have been some vote tampering or behind-the-scenes Russian influence....who knows....but none of that has been proven in a court of law...so until then, nothing changes.
We can say bad things about Trump...yada yada....but really the fault is not upon Trump. He is who he is. The fault for our present political situation is upon the political machine (individual politicians and the respective Republican and Democratic parties) that bring so-so/mediocre/unqualified candidates to the forefront for election. These politicians are paid political officials who are responsible for running our political process with integrity, skill and a duty to the citizen public.
According to our FBI and CIA, the Russians interfered with our election. Officials from those agencies have testified to that fact under oath. IMO, the election is fraud.
And Mueller hasn't been able to interview Comrade Trump because his lawyers have advised him not to since he'll get caught in lie. There was a meeting in July 2016 between Russian "cutouts" and the Trump campaign, there was a meeting in the Seychelles, which someone is talking to Mueller about, and we know of at least 4 felony convictions with Manafort likely to go to jail with the charges he has against him.
It's only a matter of time.
And you're right, Comrade Trump's approval rating remains around 40%. Now whether he can win with that same amount in 2020, we won't know until then. But we may not get to 2020 with Comrade Trump as our president.
Nonetheless, Comrade Trump won PA, WI and MI by a total of 70,000 votes, which won the electoral college. Whether or not he would win those 3 states again and FL, which was also close, based upon his disastrous 1st year, IMO, I doubt.