From Jay Cost yesterday over on the HorseRaceBlog:

Earlier in the week, I warned readers not to put too much stock into the summer polls. My argument was that voters are not paying much attention yet, and so their answers are not well-formed and possibly unstable. This is such an important feature of polling. It is really critical to bear this in mind. All of these polling numbers can change.

Knowing this fact about public opinion, one cannot help but ask whether Hillary Clinton has such a large lead over Barack Obama because voters have settled upon her, or because the press has annointed her as the frontrunner. If the latter is true, public opinion must be much less well-formed, and therefore susceptible to alteration. What happens when Obama deploys $30 million+ to move it?

The same is true of Romney's support. What happens when Romney's opponents start to spend their resources? In my initial post on the subject, I speculated that the former Massachusetts governor's strong numbers might be due to the fact that he is the only one who is spending real money on advertising. Quantification of this came from Howard Kurtz in today's Washington Post:

Former Massachusetts governor Mitt Romney has far outpaced the other candidates in ad spending, devoting $6 million to television spots, more than triple the $1.9 million spent by New Mexico Gov. Bill Richardson (D). In Iowa, said Evan Tracey, chief operating officer of the Campaign Media Analysis Group, the candidates have "blown past the historic totals of the last election" much earlier.

Among other Democrats, according to Tracey's group, Sen. Barack Obama (Ill.) has spent $1.3 million; Sen. Christopher J. Dodd (Conn.), $863,000; Clinton (N.Y.), $475,000; and former senator John Edwards (N.C.), $385,000.

That's right. Romney has spent more than every other candidate combined on campaign advertising. And so, it would be foolish to argue now that any of his leads are stable. Rudy had $18 million in cash on hand as of the last FEC report. That can change a lot of minds.

Romney has already seen his lead in New Hampshire fall from 11.8% to 4.7% in the RCP Average in the last couple of weeks. One would think his huge 16 point lead in Iowa is far from stable.