Perhaps the worst news of all for Mr. Perry, although it’s a little anecdotal at this stage, is that some of his major donors do not seem inclined to stand behind him. That could send his campaign into a death sprial, as other donors, supporters and staff jump ship. Mr. Perry does have a decent amount of cash on hand, but a fully-staffed campaign burns money quickly, especially once the actual voting nears.

If I were Mr. Perry, I would make an “all-in” bet on Iowa. Forget about the other states: you may not have the resources to compete in them anyway. Iowa Republicans have been friendly to Texans in the past, and the state can play to his strengths as a retail campaigner. More importantly, winning Iowa can provide tangible evidence that your campaign is viable, something that even Mr. Perry’s supporters must be questioning now.

Still, this is normally the strategy that a second- or third-tier candidate pursues — and not a frontrunner. If you think of Mr. Perry as a second-tier candidate, the 25-to-1 odds you can now get on him at Intrade seem roughly fair. But I’m not sure they’re a lot higher than that. It’s one thing to regain forward momentum when your campaign seems stalled, but another when it looks to be headed downhill.