Former Virginia senator Jim Webb launched his presidential campaign in July, but it's understandable if you didn't know that: for the past four months, he's kept a low profile, and the polls have reflected it. Tuesday's debate offers his first, best chance to break out of the very low single digits.

Webb is hoping to appeal to Democrats who may feel alienated by both former secretary of state Hillary Clinton and Bernie Sanders -- in particular, working-class white male voters; he wrote an entire book about the Scots-Irish roots of rural Appalachia. The former Republican's own background is in the military and the Reagan administration; he is far more focused on foreign policy than many of his Democratic rivals -- and the only Democratic candidate opposing President Obama's nuclear agreement with Iran.

If you have heard of Jim Webb, there's a good chance you're aware of an op-ed that's haunted him for years: Back in 1979, he wrote an essay arguing that women should not be allowed to serve in combat. (He said recently he is "totally comfortable" with the military deciding to allow women to serve in more roles.) He has opposed environmental regulations in coal and oil drilling, and supports expansive gun rights.

At the same time, Webb has touted his liberal bona fides -- in particular, his early opposition to the war in Iraq and his commitment in the Senate to prison reform. In speeches, he has assailed corporate tax loopholes and high CEO pay. He is critical of Obama's 2011 intervention in Libya. And he's sworn off super PACs.

Webb has not built the robust campaign apparatus most of his rivals have. Former Maryland governor Martin O'Malley, who also polls between 1 and 3 percent, has been doggedly campaigning across Iowa and New Hampshire. Webb, who has appeared in both states several times, has not done the same traditional retail campaign work. He has long expressed disdain for politics; he quit the Senate after one term. That ambivalence is a major challenge for him as a candidate -- and makes him a bit of a wild card heading into Tuesday's faceoff.