It's true that the national primary polls have consistently put Romney in the low-to-mid 20s, with Romney rarely polling above 25%. But is there any truth to the idea that there is a uniquely anti-Romney ceiling of 25% that prevents him from getting votes from the other three-quarters of Republicans? Not really. The concept is flawed for a number of reasons.
Perhaps the most important flaw in the 25% ceiling is that Romney regularly polls well above 25% in early state primary polls. As we've discussed at length in the past, polls in the early states are far more important than national primary polls: The voters in early states pay attention sooner, the candidates actually campaign there, and the results of the early state contests influence the electorate in the later states.
The New Hampshire primary polls always have Romney far above the 25% ceiling. Romney tends to poll about 40% in New Hampshire, regardless of the pollster, and across a long period of time. Indeed, Romney rarely gets below 35% in any of these polls. No other candidate has gotten such high numbers in any state.
The counterargument is that New Hampshire is unique. But there are only a few states in which the candidates are actually competing: Iowa, New Hampshire, South Carolina, Florida, and Nevada. For the most part, the candidates are currently focusing on just Iowa and New Hampshire. To suggest that New Hampshire doesn't count is effectively tossing out half the field for little or no reason. More likely, the reason that Romney does so well in New Hampshire is not that New Hampshire is so unique, but because it's the only state in which Romney has really campaigned.
The Florida primary polls have also repeatedly given Romney above 25%, particularly in October. There's been little polling in Nevada, but Romney likely gets more than his "ceiling" in that state as well.
The second big flaw in the theory is the fact that the other candidates have failed to break 25% in the national primary polls. Only Rick Perry, who enjoyed a brief honeymoon in September, managed to break 25% in the polls for awhile. If none of the other candidates can break 25%, why would Romney be the one who suffers from a ceiling? Wouldn't all of the other candidates have the same Anti-Candidate problem with 75% of the electorate?
The third problem with the ceiling theory is that it doesn't account for how difficult it is to poll more than 25% of the electorate in a multi-candidate race--especially when you throw in a large percentage of undecided voters who don't select any of the candidates. If, say, 20% of those polled are undecided, one needs to get 3/8 of the remainder to poll at a mere 30%. It's not easy to get 3/8 when there are eight candidates in the race. Getting that high essentially means you win, unless it's a two-man race.
After the first few primaries, the field will be whittled down to two or three (or perhaps one) candidates. Voters will then coalesce around the survivors and push them above 25%. The Anti-Romney vote will coalesce, but so will the Anti-Anti-Romney vote. (Which is to say, for example, if Newt Gingrich won Iowa, the Anti-Gingrich vote would coalesce around Romney in the same way that the Anti-Romney vote coalesces around Gingrich.)
Having debunked the myth of the 25% ceiling, it's also worth pointing out a historical trend: As voting day approaches, voters tend to move toward a more electable choice, even if the candidate is less exciting. Viewing the current field, the only candidate in the running who's considered very electable is Mitt Romney. His current numbers in New Hampshire guarantee him victory there, and the "strategic shift" will likely boost his numbers in Iowa, as well.