Oz, Fetterman in Dead Heat for Pennsylvania Senate Seat

The Pennsylvania Senate race is extremely close, with Democrat John Fetterman and Republican Dr. Mehmet Oz in a dead heat. Fetterman's earlier lead has vanished, and current polling shows Oz slightly ahead. The results may be delayed due to the red mirage effect, as in-person votes, which favor Republicans, are counted first. Mail-in ballots, predominantly Democratic, will take longer to count. Pennsylvania's rules prevent counting mail-in ballots before election day, and a recent court ruling may disqualify some ballots. Fetterman's debate performance, affected by a stroke, has raised concerns about his fitness, but many mail-in votes were cast before the debate.

What is the significance of the 'red mirage effect' mentioned in the context of the election?

How did John Fetterman's debate performance impact the Senate race?