Hillary Clinton maintains that she is the rightful nominee of the Democratic Party.

She bases this claim on the premise that she is the popular vote leader.

Is she the popular vote leader and if she is should we use the popular vote as the measure of the party's will?

Let's look at the numbers; according to Real Clear Politics Obama has 17,596,239 popular votes, while Hillary Clinton has 17,650,671 popular votes. Therefore Clinton has 54,432 vote margin and a claim on the nomination basis on winning the popular vote.
http://www.realclearpolitics.com/epolls/ 2008/president/democratic_vote_count.htm l

How can Obama supporters deny Hillary the nomination if she has won more votes without being anti-democratic?

There are two basic reasons for rejecting the popular vote as the measure of party will. If either if these arguments for rejecting Hillary's claim is true then Hillary's claim to "more popular votes" as the reason she is the rightful winner of the nomination is false.

If you care to hear my argument join me after the fold.

The first poll out of WV for the nomination, Rasmussen shows Clinton with a 55-27 percent lead over Obama. The primary is not until May 13th. This is the second poll I've seen recently that shows the "Economy/Jobs" issue going over 50 percent as the number one problem to solve. Here's some more: Rasmussen has more on the state of the contest today.

Bowers posted the cash on hand from 2Q ending:

Obama: $34M
Clinton: $33M
Edwards: $12M
Richardson: $7.1M
Dodd: $6.4M
Biden: $2.8M
Kucinich: $221K

In Gallup polling, Obama moved into a 30-29 lead at the beginning of June (with Gore), but since then, Gallup has shown the trend reversing and moving away from Obama. There was a lot of hope by Obama supporters that Obama would get a bounce of his fundraising totals, but the latest Gallup national poll (without Gore) shows Clinton's lead increasing from last month, and that Clinton leads Obama by 16% regardless of if Gore is in the race.

With Gore, it's a race for second place:

Clinton 37
Obama   21
Gore    16
Edwards 13

And the reason why pollsters include Gore in the race, is because at somepoint this fall Gore is going to make a decision and until then it's a possibility. But still, the story as far as the national polling goes is that the status quo is still firmly holding, and given that Gallup shows 42% of "extremely likely" primary voters saying they will support Clinton it is still Clinton's race to lose.

Research 2000 did a poll released on the Concord Monitor in NH, with these results:

Clinton          33
Obama            25
Edwards          15
Richardson        7
Dodd              3
Biden             2
Kucinich          1
Gravel            1

If Gore were also in the mix, here are the results:

                 Dec '06           July '07

Clinton          22                27
Obama            21                23
Gore             10                14
Edwards          16                10
Richardson        2                 8

On the Republican side, Romney still has the lead:

Romney           27
Giuliani         20
McCain           16
Thompson         15
Paul              1

From the last Research 2000 poll, Clinton has opened up a bit of a lead, but Obama has also increased his percentage, and Edwards falls 1% without Gore in the race 6% with Gore. The quotes in the article are amazingly anti-Edwards while pro-Clinton, hoping for Richardson, and pretty much ignoring of Obama. They also know that Romney is a loser. Dodd has moved up to 3% and Paul still is just a blip outside the internet.

Moveon held what was billed as their "Largest MoveOn Event Since 2004; Over 100,000 People Joined at 1,300 House Parties and Online to Watch Virtual Town Hall" and released the results from their straw poll on climate change:

MoveOn member vote results:
Edwards 33.10%
Kucinich 15.73%
Clinton 15.71%
Obama 15.03%
Richardson 12.60%
Biden 3.06%
Dodd 3.01%
Gravel 1.78%

You'll recall, in their last straw poll done, that Obama placed 1st, which makes his fall to a tie with Kucinich and Clinton, in 4th, surprising to some. And once again, Richardson shows he's much stronger with the members that are attending the meetings.

Votes by MoveOn members who attended house parties: 
Edwards 25.53%
Richardson 20.19%
Kucinich 17.55%
Clinton 13.80%
Obama 10.18%
Biden 6.15%
Dodd 3.63%
Gravel 2.96% 

A third and final Town Hall will take place in the fall and will focus on affordable health care for all Americans.

Because it's going to take 2157 delegates to the Democratic National Convention in August 2008 to secure the nomination and you have 138 days, from the opening of the Iowa caucuses to the closing of the polls in the California primary, to do it. You're going to have to juggle campaigns in two to three dozen states (most of them concurrent), recruiting and training thousands of volunteers and field staff. In each targeted state, you'll need to contact tens, perhaps hundreds of thousands of Democratic and Democratic-leaning voters and caucus participants, and identify those who are leaning your way and those who need a little persuasion. Then, well, you need to persuade the persuadable. Then you need to make sure you get all these identified voters and caucus participants to their polling/caucus venues on caucus and primary days. If they can't get there, they'll need rides to the polls, or maybe absentee ballots.