So he’s an Australian Russian Jew. Don’t you have to be American to be president?

The Constitution sets three requirements for the presidency: you must be a natural-born citizen, at least 35 years old, and a US resident for at least 14 years. That is the whole list. Religion, ancestry, and where your parents were born are not on it.

Ossoff was born in Atlanta, Georgia. That makes him a natural-born citizen, full stop. The Australian and Russian Jewish heritage in his family tree is just that, heritage. It carries no legal weight on his eligibility.

He did hold dual US-Australian citizenship at birth, passed down through his mother Heather Fenton, who emigrated from Australia before he was born. But that Australian citizenship lapsed years ago, and even if it had not, the Constitution says nothing about dual citizenship disqualifying anyone. What it cares about is whether you were a citizen at birth, and he was, born on American soil.

The "natural born" language in the Constitution has been tested in practice with candidates like John McCain, who was born in the Panama Canal Zone, and Ted Cruz, who was born in Canada. Both were judged eligible because citizenship by birth, whether by soil or by parentage, satisfies the requirement. Ossoff's case is simpler than either of those. He was born in Georgia.

As for being Jewish, the Constitution also explicitly bars any religious test for public office. That is in Article VI, and it applies to every office in the land.

So: American by birth, eligible by every legal standard, background irrelevant to the question. The only real barrier between him and a presidential run is winning his Senate seat this fall, and then deciding he wants to do it.