Fox News contributor Marc Thiessen joined "The Brian Kilmeade Show" Thursday to discuss why he is concerned with the chances of some Republican candidates winning key Senate races in November.

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MARC THIESSEN: Leadership is also not nominating people who can't win, I mean, and endorsing people who are the least likely to win. So, you know, maybe the red wave is strong enough that it can overcome the weakness of some of these candidates as we've chosen. There's not a single poll showing Herschel Walker ahead. There's not a single poll showing Dr. Oz ahead. I don't know how, but there's only one poll with Blake Masters, and he's losing by nine points in that. I don't know if that will work. I mean, we're we're putting ourselves in a position of losing a lot of potentially winnable races that should have been winnable. And we only need one, a net gain of one seat to take back the Senate. And the fact that that's in question, it feels like 2010. Again, we haven't nominated any witches yet, but the primary season isn't over.

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Republicans at risk of losing 'winnable' Senate races after nominating candidates 'who can't win': Thiessen

Herschel Walker, Dr. Oz and Blake Masters face uphill battles in Georgia, Pennsylvania and Arizona