I wonder if they have any idea what they've signed up for.

Being a Democrat is like traveling cross-country by bus. You end up riding with people who eat fried chicken out of greasy bags, women with wailing infants, old folks who smell like liniment, college kids whose rap or rock you can hear clearly even through the headsets they clamp tightly to their heads.

Only thing you have in common with these greasy, smelly, loud people is that you're all headed in the same direction.

It's a coalition cobbled together from loose-fitting parts. Democrats color outside the lines, rarely sing in harmony and only get along with each other as often and as much as they absolutely have to.

If I didn't value this freedom I have to drop-kick politicians of every political stripe, I'd probably be a Democrat myself.

But I fear that a lot of these new Dems, drawn largely but not entirely by the Obama campaign, are in for a rude awakening. Party politics aren't always determined democratically.

When it comes to picking the people who carry their standard, the parties' choices have more to do with winning elections than with simple math.

Which brings us to the ultimate acid test for the new Democrats: How many of them will still be on the bus in November if this race for the nomination is decided by party professionals?

The frightening prospect raised most often by the new Obama voters is that "superdelegates" may "steal" the election and thwart the will of all those people who voted for Obama.

Oh my!

Their recurrent nightmare is that the party will arrive at its convention in Denver with its work undone. Obama will lead in the popular vote, he will have a lead in the number of pledged delegates, but he will not have enough of either to close the deal.

As it stands now, his popular vote lead is only a couple of percentage points. He has more states, but Hillary Clinton has bigger states. He has the pledged delegates, but not enough to keep superdelegates from deciding it.

It opens the possibility of a brokered convention where the nomination is awarded in the kind of political game that would make the secret sessions of the College of Cardinals look like a chat room.

Whoever gets named in that process looks less than legitimate. If it's Hillary Clinton, the smell of backroom smoke would be enough to gag the Obama voters.

Up until 35 years ago, both national parties chose presidential nominees in back rooms. The primaries were little more than national polls. In local politics, both parties still choose their endorsed candidates without asking for our input.

Each of the Democratic front-runners has drawn more votes than any previous Democratic nominee. Those new voters don't want to turn on their TVs this August and hear that their votes didn't mean much.

If the party wants to hold them, both candidates need to do a better job of explaining the process than they have done so far.

Whenever I hear people talking about how superdelegates may "steal" the election, I should hear the candidate explaining how superdelegates are part of an ethical process for breaking a deadlock.

Every Democratic candidate knew the rules before he or she got into this race. They understood that if no one won the 2,025 delegates needed for nomination, the superdelegates would break the tie.

I didn't hear anyone cry about thwarting the will of the people in Texas when Clinton won the popular vote and Obama won the delegates. She couldn't whine then, and he can't whine now if superdelegates end up picking a candidate in an undecided race.

No matter which one wins the nomination or how they win it, the other candidate should be ready to campaign for the winner. They have to be ready to get their people back on the bus.

If they don't, Denver will be the end of the line for all of them. *

Send e-mail to smithel@phillynews.com or call 215-854-2512. For recent columns: http://go.philly.com/smith