"Climate change people," as 2012 presidential debate moderator Candy Crowley famously termed them, don't expect much from high-level US elections. Climate change rarely comes up, and when it does, it's usually confined to a brief bit of sloganeering.

So it's good, I suppose, that climate change finally got a decent chunk of time in Thursday night's Democratic primary debate. But I have to disagree with my esteemed fellow journalists Rebecca Leber and Robinson Meyer. It was not particularly substantive. And it was not the climate debate I've been waiting for.

It served primarily as a proxy battle, another way for Sanders to accuse Clinton of being corrupt and for her to deny it. He remained on the attack and she on the defensive, so he likely won the exchange, but on questions of climate policy it was unilluminating.

What it revealed, for the most part, are the candidates' flaws — Clinton's defensiveness and inability to articulate a broad vision; Sanders's monomania about money in politics and propensity to back whatever the left wants, even when it is mutually contradictory.

Fossil fuel influence, misunderstood

Climate was introduced through the prism of Sanders's recent attacks on Clinton regarding fossil fuel money. So, not for the first time in the debate, she started off on the defensive.

"I joined with others to try to get rid of the subsidies for Big Oil, and I have proposed that again," she said, "because that's what I think needs to be done as we transition from fossil fuels to clean energy."

This attempt to cast herself as an enemy of fossil fuel companies plays on Sanders's territory, to no particular end. Removing direct US oil subsidies would have very little effect on US emissions. The really big direct subsidies for oil are mostly in developing countries. US subsidies for oil and gas (excluding unpriced carbon emissions, which weren't included in the bill Clinton referenced) are, however obnoxious, fairly modest relative to government spending or the larger energy economy. Yanking them would be satisfying, but it would not affect change at anything like scale needed. (More on subsidies from Brad Plumer here.)

More to the point, Clinton is never going to beat Sanders at this game. Her history with fossil fuel companies, by virtue of where her career has taken her, is long, complex, and not always pretty. It is probably true that, forced to choose, they would prefer her pragmatism to his open hostility. But Sanders's specific attack is absurd.

It's about donations to Clinton's campaign (and the Super PAC supporting her campaign) from individuals employed by oil and gas companies. Clinton noted — in her oblique, difficult-to-follow way — that such donations make up a tiny fraction of her campaign haul (0.2 percent, according to Politifact).

The idea that she is selling out to fossil fuel companies because their employees are donating a relatively piddly amount to her campaign is a caricature. It's not how influence works.

Sanders, who has also accepted donations from oil and gas employees, acknowledged as much, but claimed the donations are significant nonetheless:

[A]s I understand it, 43 lobbyists for the fossil fuel industry maxed out, gave the maximum amount of money to secretary Clinton's campaign. Now, that's not saying — and then some people say, well, given the hundreds of millions of dollars she raised, it's a small amount. That's true. But that does not mean to say that the lobbyist thought she was a pretty good bet on this issue.

Notice the goal posts have moved. Sanders isn't daft enough to think this tiny amount of money (the "maximum amount" is $2,700) influences Clinton's policies, though he's artfully allowed his followers to think so. Instead he now says the donations are de facto evidence that the fossil fuel companies already think she's on their side, a "good bet."

But if the question is who the fossil fuel industry supports, surely it is relevant that 97.7 percent of oil and gas political donations this cycle have gone to Republicans.

These shape-shifting attempts to cast Clinton as in hock to fossil fuel money are only plausible if you come to the issue already convinced that she is corrupt. Absent that, the argument is threadbare. Like most of Sanders's arguments, it simply waves away the possibility that anyone could disagree with his approach for substantive or strategic reasons; only crude, dollars-for-favors corruption can explain it.

Carbon tax, imagined

Next, Sanders pressed Clinton on whether she supports a carbon tax, now widely seen as the sine qua non of serious climate policy.

She could have replied that a carbon tax is impossible under what is almost certain to be a Republican-controlled House. She could have pointed to policy proposals that would achieve substantial emission reductions by building on existing programs and authorities.

But she didn't. Instead she dodged, drifting into a tangent about the Paris climate agreement, trying to take credit for it and, absurdly, claiming that Sanders opposes it because he has said it wasn't enough. Needless to say, wanting to strengthen an agreement is not tantamount to opposing it.

She did say, in passing, "I don't take a back seat to your legislation that you've introduced, that you haven't been able to get passed." This at least gestures at the real reason she's not bothering to back a carbon tax, which is that she views it as all downside. It would rally Republican opposition, spark an endless, doomed fight with Congress, and sap time and attention from policies that might have some chance of being implemented.

Fracking, elevated

Then the discussion turned to fracking, which, for reasons unclear, has become a kind of stand-in for climate seriousness.

Asked about her support for fracking in other countries as secretary of state, Clinton stumbled through an answer, referring to natural gas as a "bridge" to clean energy, a formulation that was Democratic conventional wisdom a few years ago but has fallen out of favor on the left.

She failed to mention that EPA is working on methane regulations for new natural gas wells and that she — unlike Obama, at least so far — * supports regulating existing wells also.

Nor did she mention that an immediate fracking ban is unworkable as a matter of federal policy and would, if it actually happened, help revive coal's sagging fortunes and (at least in the short term) increase US emissions.

She didn't mention that, absent a political revolution that gives not just Democrats but anti-fracking Democrats a majority in the House, the best the next president can do is regulate fracking more tightly.

Clinton remains a frustrating candidate. She's temperamentally averse to absolutes and simple prescriptions, so she always ends up sounding lawyerly. She seems unable to mount a convincing case for incrementalism, unlike the current president, who can make incrementalism sing. She is the anti-Obama, all notes and no music.

Sanders's contradictions, unresolved

Finally, a pointed question, from reporter Errol Louis, to Sanders:

You said that climate change is the greatest threat to our nation's security. You called for a nationwide ban on fracking and phasing out all nuclear power in the US. But wouldn't those proposals drive the country back to coal and oil and actually undermine your fight against global warming?

Put aside that natural gas and nuclear power mostly substitute for coal, not oil, but Louis has a point, and it's something Sanders hasn't been pushed on.

He denied it — "no, they wouldn't" — but offered nothing in support. Louis followed up, pressing him on phasing out nuclear power. Sanders acknowledged, "You certainly don't phase nuclear out tomorrow," but didn't say when he thinks we'll have enough low-carbon power that we can take several gigawatts off the grid without raising emissions.

Sanders rejects the notion that there might be trade-offs in climate policy, but the next president is likely to face many.

Climate policy, unilluminated

The frustrating thing is that climate and energy policy is an area where the perennial debate between pragmatism and uncompromising ambition is particularly salient.

Obama began his time in office pushing a grand economy-wide solution, which was ground down and eventually killed in Congress.

Since then, building on the stimulus investments, he has undertaken an extensive series of regulations and executive actions that have arguably achieved more than the grand solution would have. Incrementalism has accumulated for Obama into a serious climate legacy.

More will certainly be needed to meet America's commitments in Paris. Clinton wants to build on Obama's progress. Sanders wants to go for another grand legislative solution. She remains unable to articulate a compelling larger vision; he remains unable to explain how he would overcome the obvious political obstacles.

When they grapple honestly with those differences — that will be the climate debate I've been waiting for.

CORRECTION, 4/17/16: Oops, I forgot that Obama endorsed methane regulations on existing wells in his recent climate accord with Canada.

It's not about saving the planet.