Previously renounced U.S. citizenship, but has since become a citizen again.
No. The US will nto allow you to gain ctizenship after you renounce it. Once you renounce your status as a US citizen, you can never be one again.
Suppose Congress passes a law stating that you can. Is their a constitutional bar?
In that case you would probably count as a naturalized citizen.
Why? You are a citizen by birth, a "natural born citizen," you are currently a citizen, and you've been here for 14 years. I'm not seeing a constitutional bar.
You stopped being a natural born citizen the instant you renounced. If you regain your citizenship you would count as a citizen by the means you regained it.
The US takes renunciation very seriously. By doing so you sever all ties with the US.
My point is, that might be in legislation, but it is
not in the Constitution. If Congress wants to pass a law (ill advised as I might think it is) that says "re-claiming" citizenship is as simple as a declaring you are citizen again, he probably could constitutionally be elected.
I can assure you, I would not support the inaction of such a law.