I don't think Iran matters, nor Israel especially, to his base. The gun control thing is about 24 hours old. The wall and the swamp maybe, but there are convenient targets for blame there.
The economy is strong, even as he's simply kicked the can down the road fiscally and jawboned the Fed to cut rates in a full employment environment. He's made progress on deregulation. He got tax reform done. North Korea is our "friend", China our enemy (which one stole American jobs)? One would think farmers would be furious losing an export market -- latest poll I saw shows 78% still support him. Consumer confidence split between red and blue is still enormous, but blue confidence has gone up more than red has gone down since the election.
I don't think he's alienated his base much personally; maybe on a few issues, but on the pocketbook issues he's been fine to this point save the tariffs and for now he's still got them convinced the pain is worth it. If anything they've formed a protective shield around him.
I agree he's lost the centrists though, which is why the Democrats need to run a centrist IMO. I think it will be too easy to galvanize his supporters and paint Sanders as a Socialist which could depress blue turnout. I agree I think Harris gives him problems. I think Biden does too, potentially, but that could go either way. Biden needs to stay above the fray and innocuous and safe and I'm not sure he will because he's older, dimmer and prone to the gaffe.
Still hoping for a late charge from Steve Bullock!
I think you underestimate the anti-Semitism in Trump's base. The cuddling up to Israel has created a ton of drama, furrowed brows and strange justifications. Many of the Drain The Swamp crowd (as I have repeatedly warned for years) jumped very easily from rich white elites to Jewish elites. You only need to spend a few minutes in his echo chambers to see it.
A significant portion of them now believe has in Israel's pocket therefore is a puppet of the Deep State.