As an admirer of Conan O’Brien, I was taken aback when a supporter accused me of bashing the latenight host, who graduates to “The Tonight Show” on June 1.

Upon further reflection, though, there was ample evidence of past misgivings in this space surrounding O’Brien’s ability to shift onto TV’s main stage. And I did speculate on whether NBC would truly let Jay Leno leave or instead swallow a hefty penalty payment to keep him, getting cold feet about O’Brien’s prospects in a three-way O’Brien-Leno-David Letterman duel.

Never mind that those qualms didn’t materialize out of thin air. They underscored a skepticism that’s increasingly common among critics — a second-guessing, “If we like it, this thing can’t possibly work” mentality.

The doubts regarding O’Brien — who’s preparing to become the fifth host of NBC’s storied latenight franchise in its 55-year history — are hardly unique in this regard. After ABC screened the pilot “Modern Family” to hearty laughter at its recent upfront presentation, another reporter instantly dismissed the show’s commercial potential despite the enthusiastic response. “That’s just for the critics,” he said.

The disconnect between critical adulation and popular success has never felt wider — fueled by an expansion of delivery systems that has helped cultivate more arthouse-type fare. This dynamic has bedeviled not merely critics but industry organizations such as those responsible for doling out the Oscars and Emmys — they’ve been left wondering if viewers will sit through award shows that heap praise upon projects with which they’re utterly unfamiliar, other than to see who wore what.

Another reason critics harbor doubts about O’Brien is that most of us who have been around that long got it so famously wrong in assessing the showdown between Letterman and Leno.

Many baby boomers bonded with Letterman during our formative years in the same way we forged emotional ties with artists like Bruce Springsteen. Leno, meanwhile, played Avis to Letterman’s Hertz — the No. 2 that tries harder — before shooting past him in the mid-1990s and remaining on top thereafter.

The search for answers as to why has been conducted mostly in hindsight, but the prevailing assumption is that while Letterman serves the stronger drink, it’s a bit too tart for mass consumption. By this reasoning, Leno goes down smoother for America’s dulled fast-food palate.

Weaned on Letterman himself, O’Brien has made clear his comedic sensibilities and preferences have always fallen squarely in the Dave camp. And because “Late Night” averages around 2 million viewers at 12:30 ayem — when viewing levels are significantly lower — he’s going to have to markedly expand his nightly audience to approach Leno’s results.

Finally, there’s a perverse aspect to critics anticipating that what we like won’t succeed — believing, based on experience, that our tastes are more refined than those of the unwashed masses. Somehow, the programs we enjoy feel more special when the world doesn’t share our enthusiasm for them. Critics doubtless supported “The Wire” with greater ferocity, for example, because it often seemed as if HBO produced the show strictly for us.

That said, it’s telling that first Letterman and now O’Brien have spoken of altering their shtick to enhance their 11:30-worthy appeal. Letterman adapted his CBS show in 1993 — including cosmetic changes, like improving his wardrobe — in the same way O’Brien is refashioning his program to suit its new timeslot and zip code. The perception lingers that what’s permissible after midnight is different — and likely affords more creative latitude — than what works segueing directly out of local news.

The wild card is that with the landscape shifting so radically, judging O’Brien’s performance promises to be especially difficult. With Leno sticking around and moving to primetime, the new “Tonight” can’t be measured against the old one, ratings-wise, any more than it can against “Late Night.”

Even before seeing the new “Tonight Show,” it’s not a huge leap to predict critics will approve. O’Brien’s past forays outside latenight — including an impressive stint hosting the 2006 Emmys — established him as a talent savvy enough to tailor his act to the venue.

Will that be sufficient to seamlessly fill Leno’s shoes? The fan in me would love to say, “Absolutely.” It’s that nagging critic’s voice that keeps saying, “Too smart for the room.”