Revolution versus evolution.
Port-side idealism versus pragmatic realism.
Heft on the left versus a breadth of depth.
Those were the choices Bernie Sanders and Hillary Clinton presented to Iowans – and beyond them, to the Democratic primary-and-caucus universe – in CNN's televised town hall on Monday night.
Their dueling perspectives were best encapsulated by two quotes.
Sanders: "We need a political revolution."
Clinton: "We need to build on [President Obama's progress] and go further."
For my money, Clinton had the best night. Not only was she poised and at ease, she actually seemed to be enjoying herself.
In this three-candidate field, her strongest pitch isn't her stand on any specific issue, but rather her experience on both the world and domestic stages, her issue expertise, and her proven political resilience. She seemed, in substance and persona, someone you could plausibly see as president.
In that light, it was interesting to watch Bernie Sanders pound away at the matter that may well have lost Clinton the 2008 nomination: Her vote for the Iraq War.
Sander's ostensible purpose was to contrast his judgment with hers, as a way to counter her foreign-policy advantage.
But the effort was just as obviously intended to pump some voltage into one of Clinton's latent vulnerabilities.
When asked about Sanders' comments, however, Clinton parried well, admitting that vote was a mistake and then noting assessments about her judgment should be based on a broader range of issues.
There, she did better in handling her negative than Sanders did in dealing with his own: his problematic record on guns, and particularly his vote to exempt the industry from liability from gun violence.
About the most Sanders can muster by way of admitting error is to say that, as president, he'd take another look at the issue.
The senator's overall message is that the changes America needs require bigger battles than Clinton is willing or able to fight – and that he's the only one with the gumption to lead the charge against Wall Street and the One Percent.
Sanders certainly has a more sweeping agenda. The primary-campaign question, however, is the degree to which that big-change agenda runs up against the voters' sense of what is politically practical or achievable.
You saw some of that when Sanders was asked how, given the nation's polarized politics, he would achieve his bold changes. His answer, in essence, was that millions of Americans would have to rise up and demand them.
That's a particularly apt question when it comes to replacing the Affordable Care Act with a single-payer health care system. Given that it has taken long decades to finally achieve near-universal-health-insurance coverage, shifting focus to fight another huge health care battle seems like textbook example of left-wing woolgathering.
That said, Sanders himself did himself some good on that issue by making the (seemingly) obvious point that though Americans would pay higher taxes under such a system, they would be relieved of the burden of their current health-insurance premiums.
As for third candidate? Well, at a time when many Americans might otherwise like to turn the generational page, the 53-year-old Martin O'Malley has managed to remain an afterthought in a race between the 68-year-old Clinton and the 74-year-old Sanders.
Mind you, I'm not a robotics engineer, but it seems to me in part that's because his sincerity-seeking-audio-modulation matrix is a second or so out of sync with his head-nodding-and-arm-gesticulations directives.
The effect doesn't render him a truly empathic figure but rather a technocrat doing his automatonic best to make a human connection.
A word about the format. No, this wasn't a debate, but it actually was quite informative. It shouldn't be a substitute for face-to-face encounters, but it certainly worked as a supplement.
And Chris Cuomo was terrific.
Good job, CNN.
Scot Lehigh can be reached at email@example.com. Follow him on Twitter at @GlobeScotLehigh.