In 2008, Democrats were fired up and ready to go, and Barack Obama cruised to a historic presidential win. In 2010, Democrats were glum, Republicans were raring to go, and the GOP won one of the biggest midterm landslides in modern history.

Which side will the enthusiasm gap favor in 2012? The jury's still out, but President Obama clearly needs to shore up his base. Young voters in particular, who turned out in droves to donate, volunteer, and vote for Obama in 2008, aren't nearly as excited this go round.

Consider one of my doctoral students at the University of California, now in her mid-20s, who voted for Obama in 2008, when she was still a college junior. This time around, however, she has vowed to vote for a third-party candidate, saying she was massively disappointed that Obama failed to live up to all the hope-and-change hype. She can quickly rattle off a list of grievances — the continuation of Bush's war on terror, the extension of the Patriot Act, the failure to close Gitmo, and the recent JOBS Act, which deregulates Wall Street in the name of creating jobs. "Last time was so exciting," she said. But now, it seems, her starry-eyed hope has turned to sadly resigned hopelessness.

Disillusioned as you may be, consider what the alternative to Obama would mean for America.

For voters of my student's generation, electing the first African-American president of the United States was a radical change, a dramatic turning point in our shared history. How do you top that? Even if the president had lived up to the massive expectations his liberal backers had for him, he couldn't recreate that same excitement in his bid for a second term. We're not making history this time around.

Well, listen up, youngsters: You ought to think again. Staying at home on election day, or casting a protest vote for a third-party candidate — that's how elections are lost. Disillusioned as you may be, consider what the alternative to Obama would mean for America.

Many progressive youngsters, including my student, are participants in or sympathizers of Occupy, the anti-bank, reform-demanding protest movement demonized by conservative Republicans and worshipped by liberal Democrats. Though Occupy has largely fallen out of the headlines, the outcry of the 99 percent against the 1 percent has not yet died out. But electing Mitt Romney — a true 1-percenter if there ever was one — would destroy Occupy. The problem is not that Romney has money, but how he has made it: Through Bain-style "vulture capitalism" and unfair tax codes. You cannot ask a guy who has gamed the system to fix the system. Obama's not exactly BFF with Occupy, and his financial reform package was not nearly as aggressive as his progressive backers would have liked. But no one can argue that the far Left would be better served on income equality by a Romney administration.

Beyond economics — an arena in which Romney is a known quantity — young voters would really be rolling the dice by abandoning Obama. Who knows what a Romney presidency would mean? In The Huffington Post, Jennifer Granholm, former governor of Michigan and now my UC colleague, calls Romney a "hollow man" — "a man without deep, longstanding conviction" who seeks the presidency "for no other reason than because there's a possibility he can win." While I agree with her assessment of Romney's hollowness, I want to remind my colleague, and my student, that the danger of such an empty vessel is that it can be filled with anything. Is that really better than a second Obama term?

The anti-Obama machine, churning out nonsense and bile from day one of his presidency, is now kicking into high gear. To counter the hundreds of millions of dollars in attack-ad-spending that the president is sure to face, Obama will need the backing of young progressives like my student. There should be no turning back. If they truly care about the left-wing ideals they espouse, they ought to mobilize for the man who — while hardly an ultra-liberal standard-bearer — is still likely to defend many principles held dear by progressives. The Republican, on the other hand, will dismantle them. Obviously, Obama has disappointed the Left. He is, after all, a politician. But he's hardly the worst politician the Left could imagine. And come November, liberals ought to remember that.