That’s pretty much the bottom line in Nate Silver’s regression analysis of the impact of 23 demographic factors on partisan voting in the 2008 election. His object was to see how much of a difference union membership makes to the likelihood of voting Democratic. The answer is: in the same ballpark as evangelicals and weekly worship attenders (God gap) were likely to vote Republican.

Of course, the relative impact of these demographic preferences varied, because the size of each group varies About 10 percent of 2008 voters were union members. Roughly a quarter were evangelicals. And nearly a half were weekly attenders. Silver calculates that the union vote boosted Obama’s (and the Democratic congressional) total by 1.2 percent. Do the arithmetic and that means a three percent boost from evangelicals and a six percent boost from weekly attenders for the GOP. Look for both of those numbers to increase in 2012.