CBS and the New York Times have a new poll out that looks at the Democratic primary race and at the general election. In the former, it uses a rather small sample, but in the latter the sample gets weighted — as usual — in favor of Democratic voters. Barack Obama has taken a lead in the national numbers for the primary, not exactly breaking news:

A new CBS News/New York Times poll finds Barack Obama with a 16-point lead over rival Hillary Clinton among Democratic primary voters nationwide.

Obama, coming off 11 straight primary and caucus victories, had the support of 54 percent of Democratic primary voters nationally. Clinton had 38 percent support.

In a CBS News poll taken three weeks ago, shortly before Super Tuesday, Obama and Clinton were tied at 41 percent. Clinton led by 15 points nationally in January.

The former first lady has lost her advantage among women, according to the poll: The two leading Democrats now have even levels of support among female primary voters.

How did CBS reach this conclusion? They polled 427 Democratic voters. That isn’t an exceptionally strong sample, and it produces a conclusion that is a likely outlier. Gallup, AP, and Rasmussen all show Obama leading but in a much closer race.

The problems increase when the poll includes Republicans. They show Obama beating John McCain by twelve points, 50-38. However, the sampling and weighting explains the strange notion that John McCain would only get 38% of a general election vote. The sample of 1152 respondents comprises 358 Republican voters, 420 Democrats, and 337 independents. Here’s how they weight the sample:

Democrats – 419
Republicans – 318
Independents – 325

Get the math? They deducted 40 Republicans, 12 independents, and a grand total of 1 Democrat for their weighted sample. The original configuration would have made Democrats 37.6% of the sample, and Republicans 32% – almost exactly how Rasmussen
breaks out party affiliation. Instead, the weighting makes Democrats 39.5% of the sample, and Republicans just a shade under 30%.

If your butcher did this, you’d demand that he take his thumb off the scale. These results are completely useless, and once again CBS and the New York Times report more on their own credibility than on the mood of the electorate.

Cross-posted at Captain’s Quarters.