He's right, of course.
The Republicans right now have a lot of fake momentum - it looks like they're gonna sweep. If they want that to translate to actual momentum, they'll have to win, and win really big. They need to pull of an opposite of 2006, or another 1994.
Which they're not going to do.
Unless they win every single seat that is up, even the ones where they have no one running, they loose? Great way to move the goalpost to keep your side from loosing.
If it makes you feel better to blame partisanship, feel free. But I'm not looking at this in terms of partisanship, I'm looking at it from a political strategy standpoint. This is very relevant to what I do for a living.
That being said, no one is expecting the Republicans to win EVERY SINGLE seat that's up... but in 2006 the Dems didn't lose a single seat or governorship - and that's not going to be true this time around.
I don't look at politics like a football game - there's no "my team". There's no where to "move the goalposts" to - because I'm not trying to "win". I'm attempting to discuss the strategy implications.