Fun With Sampling: About the Marist Poll

Receiving a lot of attention today is that McClatchy-Marist Poll which shows that Barack Obama is leading Mitt Romney 48% - 46%.  Again this is one of those cases where you can adjust a poll's sample to receive any result you want.  In the 2008 Wave Election there was a Democrat +7 electorate on election day.  This poll shows a skew is D+7 with a D/R/I of 36/29/34 among registered voters.  The more recent 2010 election was D/R/I 35/35/30.

From the Marist Poll "Most Democrats -- 85% -- are for Obama while most Republicans -- 89% -- back Romney. Independent voters divide. Among this key voting block, 48% support
Romney compared with 44% for Obama. • 92% of those who describe themselves as strong Democrats are behind Obama. Among soft Democrats, registered voters who are not strong Democrats or Democratic leaning independents, the president loses some ground. Among these
voters, 77% support Mr. Obama, and 15% are for Romney. Most strong Republicans -- 92% -- are for Romney. 83% of those who describe themselves as soft Republicans say the same.

Let's break that down:

Strong Dem:  92% Obama - 5% Romney

Soft Dem:  77% Obama - 15% Romney

Independents:  48% Romney - 44% Obama

Soft GOP:  83% Romney - 12% Obama

Strong GOP: 92% Romney -  4% Obama

Let's give each demographic 1/3 of the vote Dem = 33.3%; Independents = 33.3%; Republicans 33/3%.

The math get's a little complicated, "Remember your High School Algebra" but it breaks down like this:

• DEM (92+77)/2 *33.3% = 28.13%
• DEM 44 * 33.3% = 14.65%
• DEM (12 + 4)/2 * 33.3% = 5.32%

Total Obama = 28.13 + 14.65 + 5.32 = 48.1%

Likewise the total Romney vote, when the totals are divided up equally:

• (92 + 83)/2 * 33.3% = 29.13%
• 48 * 33.3% = 16.0%
• (5 + 15) * 33.3% = 6.66%

Total Romney =  29.13 + 16 + 6.66 = 51.8%

Difference 51.8 - 48.1 = ROMNEY +3.7%

Thus with an equal weighting 33.3 Republican 33.3% Democrat; 33.3% Independent we see that Romney is ahead by nearly 4%.  Might this be a more accurate result that a D+7 poll?