During Thursday night’s Democratic presidential debate in Las Vegas, New Mexico Gov. Bill Richardson was given a chance to answer the question about offering driver’s licenses to illegal immigrants.

Before CNN’s Wolf Blitzer turned to him, several of Richardson’s rivals had wrestled with the question that had thrown Sen. Hillary Clinton for a loop in the previous debate, triggering two weeks of complaints that she was being dodgy.

Clearly intent on setting that notion to rest, she answered this time with a monosyllable, “No.” Her governor, Eliot Spitzer, had abandoned the plan a day earlier, so she was joining the retreat.

Instead, it was Sen. Barack Obama who seemed flummoxed, At first, he acknowledged that he had voted as an Illinois state senator to require undocumented aliens to “get trained, get a license, get insurance to protect public safety.” But a moment later, confusingly, he said, “I am not proposing that that’s what we do.” And finally, he said, “Yes.”

Former Sen. John Edwards objected to the question, then said “No, but … anyone who’s on the path to earning American citizenship should be able to have a driver’s license.”

Sen. Chris Dodd said “I think driver’s licenses are the wrong thing to be doing, in terms of attracting people to come here as undocumented.”

Rep. Dennis Kucinich objected to the question because “there aren’t any illegal human beings,” and, after an irrelevant swipe at NAFTA, ended up agreeing with Edwards.

And then came Richardson, who said that four years ago, when the Legislature sent him a bill allowing illegal immigrants to obtain driver’s licenses, “I signed it. My law enforcement people said it’s a matter of public safety. … We wanted more people to be insured. When we started with this program, 33 percent of New Mexicans were uninsured. Today, it’s 11 percent. Traffic fatalities have gone down. It’s a matter of public safety. States have to act when the federal government and Congress doesn’t act (on comprehensive immigration reform).”

Blitzer then turned to Sen. Joe Biden, whose whole answer, like Clinton’s, was “No.”

The transcript notes this was followed by laughter and applause.

And, of course, none of the other candidates was ever asked, “What about the public safety argument cited by Richardson?”

That is revealing of the weakness of these debates as tools for helping voters decide which candidate to support. The TV impresarios are so eager for headlines, they rarely pause to ask the candidates for evidence to support their opinions or assertions. It is bang-bang, but rarely because-and-here’s-proof.

On driver’s licenses, Richardson offered such proof, but in another case, he did not. His “solution” to Iraq is to pull out all U.S. troops and contractors within a year and leave it to “an all-Muslim, all-Arab peacekeeping force, with some European forces, headed by the U.N.”

Well, it’s a nice idea, but such a force exists only in Richardson’s imagination – and none is likely to materialize. But he is not called upon to explain.

There are similar, if not worse, examples on the Republican side. This kind of thing makes these preprimary debates seem an exercise in theatrical artificiality, rather than substance.

Three weeks ago it was Hillary Clinton “stumbling.” Last week she was feisty and aggressive, flinging her own accusations of mud-slinging at Edwards and Obama, and finding inconsistencies in their positions.

In all the sound and fury, several important points were lost. The candidates circled around – but never directly engaged – the question of whether it is realistic, effective and practical to mandate that every family in the country obtain health insurance – and if so, how it would be financed.

As to international policy, we learned along the way that Hillary Clinton is more hard-line than her main rivals, not only on her willingness to keep a substantial residual force in Iraq, but in her belief that national security trumps human rights as a priority for American foreign policy. No Jimmy Carter, she.

But the implications of these positions go unexplored, because there’s always another candidate, another topic, another headline clamoring for attention.

I suspect these candidates are better than they have looked, and that they’d have reasons to give, if they had time to utter them. I know the voters deserve better. Can’t these debates be rescued?