A concession is merely a courtesy to congratulate the winner. That is all - nothing more and nothing less. If Mary L. conceded tonight, but somehow got more votes when all were counted, she would still win the election. What matters is the number of votes - that's all.
If Mary had conceded on Nov. 4, all that would have meant is that there would have been fewer commercials on the air (as it was, she had no money and ran only a few hundred commercials, Cassidy ran thousands). But they still would have been required to hold the election, since no one had been elected Senator. There are many races where there is only one candidate - well, they still have to hold the election since the candidate still needs to be legally elected.
She could have resigned her seat and allowed Gov. Jindal to name Cassidy.
This runoff was really unnecessary when she got 2% more than she did in November.
Are you sure?
I used to live there.
I recall a (white) judge who actually won the primary - a black finished second (both candidates women as I recall).
Anyway the campaign got so ugly that the white woman withdrew. The second place candidate was the automatic winner.
Now that was a local race not a federal one.
Oh I think I misread your post. If the concession occurs more than X days before the election the runoff is not held.