So Who's Next Out Of The Clown Car?

Good question.  The Washington Post's Philip Bump crunches the numbers in the aftermath of Scott Walker's disastrous run:

Walker, like many other candidates, saw a bump in the polls shortly after he announced. But the top of that bump wasn't as high as his poll numbers had reached earlier on either nationally or in Iowa, where he was consistently the front-runner for months. He announced, he got the bump -- and then it vanished. 

The vanishing, it's worth noting, happened shortly after the first debate, in which Walker offered an unimpressive performance. 

That sort of erosion isn't as common as it seems. Rick Perry saw it in 2012. Rudy Giuliani saw it when the bottom fell out in 2008. Usually, fade-outs are less steep and more extended. Walker plummeted.

Specifically, Bump found the high point of Walker's national polling since announcing and measured the change in that number, then did that for the rest of the GOP field.

Walker and Perry had the worst drops in national polling averages since announcing.  They are both now out.

The lowest-performing candidate left is now Rand Paul, but the continual zero candidates (Gilmore, Graham, Pataki, Jindal) are still at zero too.  There's not too much pressure on people who started with nothing to leave, they can only go up (case in point, Fiorina.)  However, these guys are to the point of desperation now, needing attention and donors, and are willing to say whatever they need to in order to get both.

Also, both candidates out have been governors who couldn't catch on nationally.  That means Santorum or Christie.

I think Rand Paul will stick around.  He's already invested a lot of cash in his Kentucky GOP caucus scheme in order to be able to run for both offices, dropping out before the caucus and he loses his investment (and he's got his dad's network to fall back on.)  Besides, like the other sitting GOP senators in the race, he's still got his cards to play during the upcoming Shutdown Season, something Perry and Walker didn't have.

Santorum on the other hand, well, let's just say the guy knows what losing looks like, because he's been there before, and he's there now.

I'd keep an eye on him being the next out, if I had to venture a guess.

Going in the other direction, well, it's Trump, Fiorina, and Carson, the three candidates who haven't held office.  Seeing Kasich and Cruz be the only two politicians in office who have improved their positions since announcing is notable.

Keep an eye on them, too.