The Weighted Popular Vote (WPV) is very simple. I take the population of each state in the 2000 census, and multiply it by the percentage of votes each candidate gets in the state (excluding Michigan and Florida, since they have not yet held a valid vote). This allows us to compensate for the inevitably lower levels of voting in a caucus, since it is held at a particular time and lasts for a lengthy period.

There’s a big problem with the common measurement of the popular votes, since it disenfranchises the states which held a caucus. For example, Colorado (pop. 4.3 million) with 120,000 caucus voters, counts under the popular votes analysis for less than a third of the value of a much smaller state, Oklahoma (pop. 3.45 million) with its 417,000 primary voters. The weighted popular vote compensates for this.

So here are the results: by the WPV, Obama leads Clinton 110,761,104 to 98,744,197 (52.87% to 47.13%, a margin of 5.74 percentage points). By contrast, the current popular vote summary has Obama leading Clinton 51.38% to 48.62%, a margin of 2.76 percentage points (often reported as a 49-47 lead in most of the media). By the regular popular vote margin, Clinton would need to gain 720,000 votes to catch Obama. However, if we apply the WPV percentage margins to the number of current votes, Clinton would actually need to win by a margin of 1.49 million votes to equal Obama.

The remaining states (and Puerto Rico and Guam) have a total population of 41,252,457. Utilizing the WPV, Clinton must win these elections by a total average margin of 64.5% to 35.5%. That means Clinton must win by a margin of 29 percentage points just to equal Obama in the real, weighted popular vote. Considering that Pennsylvania is a strong state for Clinton, and she is behind in several remaining states, it is likely that even a 40-point win by Clinton in Pennsylvania would leave her unable to catch up to Obama in the pledged delegates or the weighted popular vote. In other words, Clinton cannot win.

Of course, the only real measure of victory in the Democratic primary is the number of pledged delegates, not the number of states or the popular vote. But it is valuable to look at the popular vote, as long as you weight the margin for the caucus states.

This also allows us to test whether Obama’s lead reflects the oddities of the delegate allocation system (as happened in Nevada, where Clinton won the popular vote but Obama won more delegates). The WPV shows us that this hasn’t happened. So far among the pledged delegates, Obama has won 52.66% compared to Clinton’s 46.56%. This delegate victory margin of 6.1 points is roughly the same as the WPV’s margin of 5.7 points.

Of course, some people might object to the caucus system altogether. But those were the rules adopted by both parties to allow them, and caucuses have the benefit of helping to build party involvement and reducing the influx of Rush Limbaugh acolytes trying to bring chaos to the Democratic primaries. If we are going to have caucuses as part of the primary system, then the Weighted Popular Vote is the only fair way to measure the overall national popular vote.

Crossposted at ObamaPolitics.