Numerous polls show a sizable percentage of Democrats saying they would either vote for John McCain or not vote at all in the general election if their candidate does not win their party's nomination. History shows that, in the end, most unite around the nominee, but even if 10 percent desert their party or stay home, that could be the deciding factor in a close election.
For now, it seems, the Democrats' long nominating race comes down to a floating mathematical equation that by itself engenders suspicions on both sides. Since January, when the first caucuses and primaries started, the delegate toll needed to win was 2,025.
But Clinton's campaign this week, seemingly moving the goal posts further downfield, said the magic number will likely be higher than that when the party eventually agrees to seat and apportion the disputed Michigan and Florida delegations.
Plans are circulating behind the scenes to seat both delegations and to apportion about half their delegates between the candidates. That could push the nominating number up by a couple of hundred votes.
One proposal on the front burner would apportion the added delegate numbers so that they would not necessarily change the dynamics of the race and reflect the primary wins of both candidates.
Absent from all the daily reporting on the Democrats' race is the key word "proportional," which describes the excessively egalitarian system in which both candidates end up with a big share of the delegates in each contest.
Clinton campaign strategists think she will be able to eat into Obama's lead over the remaining six contests, ending in Puerto Rico on June 1.
By that time, strategists who have crunched the numbers told me that she'll be closer to Obama's lead but still behind him.
"I think that when this is over, Obama will still have a lead in pledged delegates because of the party's proportional system," Grossman said. "But I suggest she will narrow the gap and she will win the popular vote, and she will be able to demonstrate after June 3 that she is the best candidate to put up against McCain.
"The uncommitted superdelegates would be the ones to put her over the top," he said, though he acknowledges that would also require getting some "delegates to switch sides."
That's when Grossman's worst fears could come true.