RALEIGH – The number to watch for assessing the prospects of Hillary Clinton’s now-longshot campaign for the Democratic presidential nomination is not the pledged-delegate count. It’s not the national opinion polls, either the spread against Barack Obama or the fall hypotheticals against John McCain. It’s not the number of state contests that each candidate has won. And it’s not the fundraising take.

The number to watch is the estimated, accumulated popular vote in Democratic primaries and caucuses, including Florida.

Let’s break this phrase down. First, the popular vote must be estimated because four states – Iowa, Nevada, Maine, and Washington – have not released actual vote counts from their caucuses. There are several vote estimates out there for the four states, but most people seem to be citing the Real Clear Politics tally, which is fine with me because I’ve been a longtime user and booster of the site.

Second, an accumulation of the popular vote gives proper weight to the preferences of Democratic voters as a whole, rather than letting the party’s sometimes-bizarre weighting system distort the picture.

Third, the popular vote is the key metric now because of the nature of Clinton’s last pitch to the superdelegates, who will select the nominee. If by winning sizable victories in Pennsylvania, Indiana, Kentucky, West Virginia, and Puerto Rico, and keeping Obama’s victory margins in North Carolina, Oregon, and elsewhere modest, Clinton ekes out a popular-vote majority, she hopes to morph into Al Gore. That is, she wants the Democratic officeholders and functionaries who form the ranks of the superdelegates to hear an echo of Gore’s 2000 complaint and to fear that rank-and-file Democrats will perceive a similar injustice.

Yes, Clinton is also arguing that she would be a better general-election candidate against McCain, but that’s a bit speculative. Using national and state-by-state polls, one can construct a case either way. What would help Clinton sell her scenario is to be able to say, “Not only are there good reasons why I the most competitive candidate for Democrats, but most Democratic voters agree with me.”

Fourth, and perhaps most importantly, the vote tally Clinton will cite, with some justification, will include her significant win in the January 29 Florida Primary. Naturally, she’d like to throw in Michigan, too. But the two cases are dissimilar. Although both candidates said they would honor the national party’s sanctions against Florida for moving its contest early, both candidates were listed on the ballot. Neither ran full-bore, well-funded campaigns in the state. In Michigan, however, Clinton was on the ballot but Obama was not. Attributing the non-Clinton votes to Obama is one way to try to add Michigan in, but it ignores the fact that Obama voters were more likely than Clinton voters to stay home on January 15, not thinking that it was worth the bother.

According to the current RCP count, then, the popular vote tally with Florida stands at Obama with 14,265,507 and Clinton with 13,732,971. His margin of 532,536 is sizable – nearly two percent – but not yet insurmountable.

I know that annoys and angers Obama supporters. Some are so bitter about it that they cling religiously to the pledged-delegate count as the only relevant statistic. If Clinton nets several hundred thousand votes in Pennsylvania next week, however, she will still be in the hunt.

Hood is president of the John Locke Foundation.