Tonight’s Democratic presidential debate could be nothing less than a battle for the soul of the party and the love of its base.

There’s a strong Democratic candidate representing the party’s left wing, a guy who wants a big, high-tax federal government that provides lots of benefits, cracks down on Wall Street and doesn’t generally bomb stuff. Sen.  Bernie Sanders of Vermont is garnering a lot of money and some big crowds with a message he’s been delivering, practically verbatim, for the past  40 years. But for 39 years hardly anyone paid attention. Now, he’s  on the big stage under a red-hot national media spotlight for the first time, facing direct competition eager to bring him back down to electoral earth.

No one is quite certain how far Hillary Clinton will go to the left to head Sanders off. She does not believe a huge leftward shift of the country’s governance is possible, and she does not believe a candidate who fights for that is electable. She takes tons of money from Wall Street, which can certainly change one’s perspective.

CommentaryChiusano: Finding dignity in baseball and politicsMore coverageOpinion and analysis about the 2016 presidential campaign

The real question isn’t just where the candidates position themselves, but where Democrats want them positioned. No one really knows the answer yet. Tonight is about beginning to find out.

And to a lesser extent, the debate is  going to be about three no-hope candidates trying to make a ripple and catch a wave. Former Baltimore mayor and Maryland governor Martin O’Malley gives wise moderate, totally unmemorable speeches about his dream for America. So expect to see that tonight.

Lincoln Chafee is a former mayor, governor, and senator, who thinks it’s unfair that his candidacy isn’t being taken more seriously. The Rhode Islander will be looking to introduce himself to the nation tonight.

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Jim Webb, the former senator from Virginia, will also be there. All three will have to decide whether to go for dignified party elder status or a “ferocious pitbull who refuses to go unnoticed” designation.

And over it all will loom the ghost of Vice President Joe Biden, haunting the proceedings with the specter of a possible run.

So while the proceedings don’t have the sizzle of a Trumptacular Republican debate, tonight could tell us a lot about the Democrats will face 2016.