According to fivethirtyeight Trump’s biggest gap in approval/disapproval (-20 points) happened when GOP was trying to repeal Obamacare and when they were passing tax cut bill (July and Dec of 2017). His most narrow gap (under minus 10 points) happened during the whole immigration debacle. (I’m pretty sure it was a brainchild of a couple of guys named Steve). You see a pattern here? Immigration in the news plays into their hands; Healthcare and tax cuts going to 1% is what can bring people to the polls.
Add the issue of corruption to the mix, as it has been gaining traction with voters, and you have a winning formula.
Left with Balls 
And, unfortunately, Democrats are starting to march into the Open Borders/Abolish ICE trap – a trap, because only a small portion of American population actually supports open immigration, and a significant portion of those supporters aren’t even eligible to vote themselves.
It’s madness. GOP is lucky in many respects, but especially in having such a clueless opposition. Dems have no killer instinct when it comes to politics, to winning. Sigh.