They don't have to get more than 50% in the final race, just a plurality. That's how x42 was able to be President even though he only got 43% of the vote in his first Presidential election.
x42 won because he received a majority of the electoral votes. Popular vote means nothing in a Presidential election.
Congressional and Senate races on the other hand, are determined by state law. GA requires 50% VA apparently does not, as other have said.