Whose Congress?
Likely a Republican Congress but what sort of Republicans? Rinos?
Will Rino Republicans break their lifelong habits and decline to combine with Democrats to give Trump his way contrary to the Constitution, in favor of crony capitalism?
I fear relying on Congress to save the Constitution from Trump is about as futile as relying on Congress to save the Constitution from Barack Obama.
Mostly those are two different things. Trump will support some crony capitalism and we can't count on politicians to save us. But Trump might also do some surveillance or something like that. Although I would say he is much more inclined to keep potential terrorists out (e.g. Muslims) than increase surveillance. But that aside, let's say Trump decides that surveillance is cool and we should do more. That would require approval and oversight by congress. We should have a left-right coalition against that. The second most popular candidate in the race is an anti-surveillance leftist. The American people need to avail themselves of their political power to stop things like that, we can't expect any president to control the bloated apparatus of federal government.