Talk about putting a thumb on the scale...

Weekly Standard:

Since about the beginning of President Obama's tenure, the Gallup poll has generally been one of the least positive polls for the Democratic party. This has prompted outrage and pressure from the left--even from presidential advisor David Axelrod.

Over the summer Mark Blumenthal of Huffington Post wrote a critique of Gallup's daily presidential job approval poll. The point of which was that Gallup was over-sampling whites and thus understating President Obama's position in the adult population. I responded by arguing that Blumenthal's case was underdeveloped and less-than-met-the-eye, and that was basically where things stood.

Until, that is, this week. President Obama enjoyed a bounce in his Gallup job approval number after the Democratic National Convention, as was to be expected, but there was a twist: it did not disappear. And while Gallup on average had found Obama's job approval around 47 percent with adults through most of 2012, for the last five weeks it has been regularly above 50 percent. Yesterday, it stood at 53 percent, a number we have not really seen since 2009.

Unusual. So, what's going on? Alan Abramowitz of Huffington Post and The Democratic Strategist noticed that Gallup has increased its share of nonwhites from 27 percent the week of the convention to 32 percent last week, a nearly 20 percent boost. In other words, Gallup seemed to have tweaked its methodology with just weeks to go until Election Day to reflect the criticism that has come from the left.

This is about as bad as it gets, polling wise, although Gallup can claim that there is a great debate among psephologists and pollsters just how much sampling should be done via cell phone and how much via land lines. Census data shows that there are a large number of Americans who have no land line at all - many of them minorities. Upping the number of cell phones sampled can be justified on those grounds, but one could easily question the timing as well as whether it is proper for a polling organization to respond to organized pressure from one party or the other.

AT Political Correspondent Rich Baehr breaks it down:

Romney gets about 60% of whites, and no better than 20% of minorities. This means the 5 point shift should compute to Obama getting 2% more, and Romney 2% less, or a 4 point margin shift between the two on average (the 5 point shift broke 3 to 2 for romney and now 4 to 1 for obama).

Jay Cost:

Back in June, I thought there was less than met the eye to Blumenthal's critiques of Gallup. And I thought Gallup thought the same thing. Maybe the polling outlet changed its mind. Maybe it had other reasons for making the change. Who knows? That stuff is all "black box," proprietary methodology that is not open for public analysis.

What I can say is that it's problematic to alter one's methodological approach to polling elections just five weeks before the biggest election in a generation. In fact, I think this is a highly inopportune time to make such a change; do it in the summer of 2012 or the winter of 2013, but for goodness sake not the fall of 2012!

As long as they change the weighting system along with the sampling, theoretically, it shouldn't change the outcome. But weighting is something an art form and the likelihood that this change will skew results is pretty high.

Rich Baehr adds this:

In 2008, white voters were 74% of the electorate according to the exit polls, and minority voters were 26%. Before the adjustment, Gallup had white voters at 73%, minority voters at 27%. After the adjustment, white voters were 68%, minority voters 32%. Most analysts believe that due to an enthusiasm gap favoring Republicans this time around (unlikein 2008), white voter share in 2012 might be in the mid 70% range, about where it was last time, maybe even a bit higher, overcoming any demographic shifts that have occurred in the last 4 years. But white turnout as 68% of he total? Doubtful.