TALLAHASSEE, Fla. — Amid the blur of lawsuits and noise around the recount in Florida’s Senate race lies a possible outcome that could be the ultimate twist: Senator Bill Nelson may not win the election, even if he wins the election.

That is because the Constitution says that the ultimate arbiter of who gets a Senate seat is the Senate itself — not election officials or the courts.

That would not seem to bode well for the Democrats or their incumbent, Mr. Nelson. Though he trails his Republican opponent, Gov. Rick Scott, the margin has dwindled to about 13,000 votes; Mr. Nelson hopes to make that up in the recount and take the lead.

If that were to happen, though, it is not unthinkable that Republicans would consider using their majority power in the Senate to refuse to seat Mr. Nelson and to give the seat to Mr. Scott instead — especially considering how he and his party have repeatedly insisted, without offering evidence, that the ballot review process has been riddled with fraud and misconduct.