I think my idea for this is that a candidate doesn’t win the election unless they get more than 50% of all eligible votes, not 50% of the votes cast. If there is no clear winner the seat is vacant, but a new election is scheduled for two weeks later. Districts and states that don’t care to vote simply don’t get a say.
What if people keep not voting? Surely you'd also have to compel voting to make this work.
And what if there are, say, ten candidates?