Welcome to the alternate universe. The world we've all been waiting for. The debate without Trump.

The most important storyline coming out of last night's GOP debate — the final before the Iowa caucuses — is that with Trump gone, the debate was a monumental bore.

There was one exception, of course. Because as one of the two most interesting candidates deserted the stage, the other came back — in the most brilliant combination of high dudgeon and medium chill the debates have seen.

Rand Paul returned: from his exile as the undercard participant he refused to be and from the Sargasso Sea into which his candidacy, through no real fault of his own, had sunken.

For that you can credit two things. First was Paul's own demeanor, cleansed in the purifying fire of having nothing to lose and nothing to perform or project. Relaxed, confident, clear, and — as we say — "himself," Paul slid into his zone early. He set the tone with the night's lone defense of leaving mosques open (this is what it's come to — without Trump), then rammed the civil-society theme home by mounting the field's only defense of reforming America's sad and ungodly prison state.

Delivering these lines with the kind of credible insouciance usually reserved for Owen Wilson is beyond the calling of the rest of the Republican field. For Paul it came off as natural as his ringlets.

Then there was the Islamic State. Analysts have pondered why Paul's campaign — once flagged as a top-tier operation in meaningfulness and buzzworthiness — dropped off so precipitously. Some have laughed that even the Republican most like Bernie Sanders, in his authenticity and directness on the issue of simple justice, still polls in the single digits. But Paul's struggles can be traced, I think, to a single source — the rise of the Islamic State, which blossomed, in a wan irony, under the very foreign policy Paul himself decries.

Islamic State panic — as far as panics go, reasonable enough — sucked the wind out of Paul's comprehensively libertarian approach to the Republican campaign. You just can't talk about American Muslims and African-Americans when public opinion has screwed itself into the dark certainty that a third-generation foe has overwhelmed us all.

What a pity it is: Marco Rubio, whose fortunes could have soared beyond any caliphate's wildest dreams, strained last night as he has through this race to recoup his lost Tea Party cred by outdoing Trump, Cruz, and Bush in foreign-policy vitriol. He might as well have responded to his toughest question of the night by intoning, "You know who I've never supported amnesty for? ISIS."

Rubio received accolades for squiggling out from under the enormous anvil moderator Megyn Kelly had dropped over him in the form of that amnesty question. But why Republicans should put their faith in a boy wonder who can artfully dodge on every issue but his faith in Christ remained as open a question now as it did last week. And the caucuses are nigh.

What a pity, too, it is for Cruz, whose ebullient rehearsal of his carpet bomb fantasy utterly failed. Cruz whiffed as hard in this debate as Rubio, albeit in different ways. No surprise that Paul's most piercing moment came by linking — as, bizarrely, no other candidate quite has managed — Cruz's reputation for vanity with his reputation for calculation.

Superficially, Trump's absence made for a more reasonable, adult debate. But it was also more hollow. The shadow proves the sunshine.

Despite the conservative bona fides paraded on stage, it is Trump and Paul who cut through the peacocking that passes too easily for politics in this field. And last night, whoever "won," there were too little of either candidate for Republican voters to know what is going to become of their party.