True story: After this post was published this afternoon, I scolded myself for suggesting Walker might be out of the race by Halloween. “C’mon, man. It’s Scott Walker. He’ll make it to Iowa.” Two hours later, here we are.

People on Twitter are comparing this to Pawlenty’s flameout in 2011. It’s much, much worse than that, I think.

Gov. Scott Walker of Wisconsin has concluded he no longer has a path to the Republican presidential nomination and plans to drop out of the 2016 campaign, according to three Republicans familiar with his decision, who spoke on condition of anonymity.

Mr. Walker called a news conference in Madison at 6 p.m. Eastern time.

“The short answer is money,” said a supporter of Mr. Walker’s who was briefed on the decision. “He’s made a decision not to limp into Iowa.”

Mr. Walker’s intended withdrawal is a humiliating climb down for a Republican governor once seen as all but politically invincible.

I’m stunned. Pawlenty, for all his good points, was never a conservative rock star. He never had a world-beating accomplishment as governor to rival Walker’s demolition of PEUs in Wisconsin. And he was never on top of the polls even in the earliest stages of the campaign. Pawlenty was always a can-he-or-can’t-he question mark: Can he break out from his midwestern anonymity and challenge Mitt for the nomination? He had all the credentials to be a solid consensus nominee, but he was a longshot. Walker was not a longshot. He was top tier from day one. In fact, if you polled most pros on how they saw the race going, I’d bet a majority would have told you that Bush would bigfoot Rubio and Walker would take care of Cruz in Iowa and it would come down to Jeb and Scott. As recently as three months ago, there was every reason to think that would happen.

And then Trump got in.

Walker’s set to speak at a presser at 6 p.m. ET. Stand by for updates, which are surely coming.

Update: The NYT just added this.

“Donors have totally dried up for Walker, and getting people to come on Thursday [to a fundraiser in New York] was unbelievably hard,” said one of the donors. “Everyone I know was just totally stunned by how difficult the fund-raising became, but the candidate and the campaign just couldn’t inspire confidence.”

That seems paradoxical in an age when campaign-finance rules have made it easier than ever for one or two charitable billionaires to singlehandedly keep a candidate going. But I think it’s easily explained: The field is so large that there’s no end of alternatives for a disgruntled donor who’s hoping for a better return on his dollar. If you like Walker, chances are you also like Rubio and Bush and Fiorina and even Christie. He pulled an asterisk in the last CNN national poll. Why ride down to the bottom with him when there’s still time to get in early-ish on a campaign like Rubio’s with a better chance of winning?

Political junkies are invited to let me know if there’s ever been a flameout as spectacular as Walker’s in a primary. Again, this guy was universally understood to be top-tier. Even now, his favorable rating among GOPers in most polls is solid. He simply can’t get anyone to prefer him to everyone else in the field after a long summer spent reversing himself on seemingly every difficult campaign question. As it is, Chris Christie lasted longer in the primaries than Walker did. On New Year’s Day this year, not one pundit in America would have predicted that.

Update: It’s conventional wisdom that Trump owes his lead to his hardline stance on illegal immigration. Walker took a hardline stance too, not just on illegals but on reducing legal immigration to protect American wages. Why did it work for Trump but not for Walker?

Update: Anyone want to hire a newly unemployed Walker staffer?

I will never, never understand the "It's an arms race to grab the staffers who tanked this campaign" mentality

— PoliMath (@politicalmath) September 21, 2015

I doubt Walker will endorse anytime soon — like his donors, he’s now in a position of needing to pick a winner too — but given all the nice things he’s had to say about Rubio, I’d assume he’s leaning that way. Or maybe he just won’t endorse at all and will wait for his inevitable appointment as Labor secretary by whoever the next Republican president is.

Update: There’s truth in this:

In the end, Walker's greatest strength, the idea that he'd hold fast in a fight, undid him because he simply didn't on too many issues.

— Drew McCoy (@_Drew_McCoy_) September 21, 2015

Walker’s much squishier than I am on immigration but he would have been better off sticking with his true position than tacking right to try to pander to people like me. Be the guy you are and you’ll earn some respect even when voters disagree. As it is, he came off as someone who was saying whatever he thought Republicans would want to hear — ironically, more Romneyesque than Pawlentyesque. How do you a trust a guy like that to hold a firm line on amnesty?

Update: First Perry, then Walker:

It looks like the more successful your conservative accomplishments, the worse you do in 2016. With that in mind I declare my candidacy.

— Dave Weigel (@daveweigel) September 21, 2015

Who’s next by that metric? Jindal? Let’s get all of the conservative governors who’d do a good job as president out of the race so that we can concentrate on Trump.

Update: Walker’s donors are leaning exactly the way you’d expect, says Erick Erickson

I spent that night and the next day talking to some of Walker’s more prominent supporters. To a person, they were all for Rubio second and many of them were headed that way after Walker’s debate performance.

I suspect that will hold and many, though not all, of Walker’s donors will go with Marco Rubio next.