Watching the Democratic primary contest can feel like reading a bad murder mystery. You may encounter some plot twists and surprises, but the end seems obvious. The butler did it. Hillary Clinton will win the nomination.  Ruth Marcus is a columnist for The Post, specializing in American politics and domestic policy.  On a deeper level, though, the contest is more subtle and more interesting — more Jane Austen than John Grisham. Indeed, dear reader, the day after the Democratic debate, Austen herself was invoked by philosopher Cornel West, standing in for Sen. Bernie Sanders (I-Vt.) and jabbing at the woman he called “sister Hillary,” with her “lip service” to progressive causes.  “My question for Hillary Clinton is what I would call the Jane Austen challenge,” West said. Austen “talked about ‘constancy,’ ” he noted, making what is surely the first reference in the history of the Iowa caucuses to Fanny Price, the prim heroine of “Mansfield Park.”  “And what is constancy,” West continued, stretching out the sibilant syllables with his preacherly delivery, “but a willingness to act for integrity, sustain moral engagement and always subordinating political calculation to deep conviction?”  If the audience was puzzled by the literary allusions — we were, after all, eating barbecue in a dirt-floor livestock arena — West’s point about Clintonian calculation was clear.  Inconstancy is the constant theme of modern politics; it is a truth universally acknowledged that flip-flop attacks work. But something else, deeper and more significant, is taking place in the Democratic race.  To quote Austen in “Sense and Sensibility” (erudition courtesy of my late colleague Mary McGrory, who would have been overjoyed to hear Austen on the campaign trail), Sanders is paying Clinton “the compliment of rational opposition.”  More opposition, indeed, than we have become accustomed to in Democratic primaries. Saturday’s debate revealed this essential truth. The ideological gulf between Sanders and Clinton is as wide between two front-runners as in any Democratic campaign in decades. Sanders doesn’t want to talk about her damn e-mails. He wants to talk about her damn worldview.  Clinton is a methodical reformer, a pragmatic tinkerer, by virtue of both personal temperament and political necessity. Sanders is an unabashed revolutionary. She would fiddle with Obamacare; he would junk it for a single-payer system. She would tighten Dodd-Frank; he would bust up the big banks. She sees the system as imperfect; he sees it as rigged.  Not that the party has marched in ideological lockstep — these are Democrats, after all. But you have to go back at least to Walter Mondale vs. Gary Hart in 1984 to find this great an ideological divide, and by comparison even that seems rather “vanilla,” to use West’s description of Iowa.  Back then, the old-line liberal beat the candidate of new, if somewhat indistinct, ideas. (Recall Mondale’s “where’s the beef?” zinger, or look it up if you’re not old enough to remember.) This year, the far more liberal candidate is the much longer shot.  Sen. Bernie Sanders (I-Vt.) compared himself to former president Dwight D. Eisenhower during the Democratic presidential debate at Drake University in Des Moines, Iowa. (CBS)  But that does not render Sanders irrelevant. First, he has nudged Clinton perceptibly leftward, if not so far left as to pose a general-election threat. Without prodding from Sanders, would Clinton have come out in opposition to the Keystone XL pipeline or the Trans-Pacific Partnership? Counterintuitively, Sanders’s presence also has served to highlight Clinton’s more liberal positions on gun control, as she has deployed that issue to underscore her liberal bona fides and undercut Sanders.  Second, and more importantly, Sanders’s candidacy illuminates and intensifies a fundamental division within the Democratic Party. In his heart, I suspect, Sanders knows he will not be the nominee, much less the next president, but that does not mean he is wasting his time.  The significance of Sanders is to hone and highlight the debate over the future path of the Democratic Party and the correct approach to curing the country’s ills. Is the system dangerously tilted in favor of what Sanders terms “the billionaire class,” and the fix therefore primarily redistributive? Or, as centrist Democratic groups such as Third Way contend, has the modern global economy fundamentally changed in ways that require expanding opportunity for participation, not simply rearranging stacked deck chairs? Where, precisely, does Clinton herself stand?  Sen. Elizabeth Warren (D-Mass.) helped ignite this intramural argument. Yet for Sanders to wage it on a presidential level brings a new intensity to a dispute that seems destined to endure beyond Election Day, unresolved by either a Clinton election or a Clinton defeat.  Read more from Ruth Marcus’s archive, follow her on Twitter or subscribe to her updates on Facebook.
Hillary Clinton may be inevitable, but the Vermont senator has opened a true debate in the Democratic Party.