When surveys are conducted, the people who are interviewed are randomly selected registered (in a good poll) likely voters who are willing to respond. But that just begins the process. Those responses must then be "weighted" or allocated based on some projected model of past or future voter turnout strength. In other words, those conducting the poll must adjust the numbers to reflect the percentage of men, women, Republicans, Democrats, Independents, Whites, African-Americans and other groups such as Hispanic-Latinos who will likely vote in the contest.
This is no easy business, and it is why polling is as much an art as it is a science. But there are some ways to get to these determinations, such as polling a state and asking which party voters identify with separately and before the actual "ballot test" survey is taken. But enough of these geeky polling details.
I have in my gut a belief that the polls we are seeing now underrate Romney's strength. For example, we saw a hugely enthusiastic young voter turnout for Obama in 2008. As a result, polls were weighted to give more voter strength to the category of 18- to 29-year-olds than in past years. In general, younger voters just do not turn out to vote.
This year, I am seeing evidence that the enthusiastic and energetic vote of young Americans for Barack Obama has at the very least lost some of its mojo. That likely means they are not as excited about voting. So, an adjustment in the "weighting" of a survey by a reasonable number of percentage points downward for that group could mean the difference in some of these critical "swing" states between Obama being up by one point and Romney being ahead by a percentage point or two.
Another group that likely needs some "tweaking" by pollsters this go-round are those who identify themselves as "independent" voters. In 2008, they helped decide the presidential race, as a significant percentage were sick of the Bush years and were desperate for any type of "change" they could believe in, so to speak. This year, we have more voters than ever identifying themselves as independents. This is surely a result of their absolute frustration with a Congress that appears to be chasing its tail and producing nothing of value.