You can’t help but root for any romantic comedy that comes along to work, because so very few of them do.

“The Right One” has a few promising elements which make themselves obvious from the get-go. But the good ideas run out quickly and the cute scenes turn few and far between long before we’ve taken that first peek at our digital watch.

And that chemistry we get a whiff of between the stars remains just that, a whiff — as in a swing-and-a-miss.

Cleopatra Coleman of “The Argument” and TV’s “The Last Man on Earth” makes a perfectly bubbly leading lady, a romance novelist with writer’s block. Sarah needs to get inspired, get writing and get her next book in the stores because her agent Kelly (Iliza Shlesinger) says “You’re almost 30. It’s my last chance to sell you as ‘a prodigy.'”

“I’m 31!“

She needs to get over her last break-up, Simon, get out there and get her mojo back.

That’s how she starts running into this mysterious stranger played by Nick Thune of TV’s “Life in Pieces” and “Love Life.”

First, he’s a pretentious art critic at a gallery opening she and Kelly drop in on. Later he poses as a pretentious artist, with a minor wardrobe change and serious upping of his poseur game.

“I before ‘me,’ except after ‘you,’ THAT’s what this painting is about!”

Running into him busking as ‘Cowboy Cody’ in a city square (set in Seattle, filmed mostly in Vancouver), doesn’t get any answers in the face of her persistent questions. He cryptically suggests he’ll be at a performance space that night, and she winds up ditching her set-up date after catching his wigged, cross-dressing (he has a beard) impersonation of a singer-songwriter “gal” fresh off the bus from Tulsa.

Sarah is hooked. And as we’ve seen this guy at his day job, gonzo skateboarding free-spirit “G-Money” at his phone sales office, and volunteering as puppeteer Mr. G at a preschool, we’re at least intrigued.

Whoever this “G” is, he’s damned good at becoming whoever his costumer will bond with and buy from on the phone — a master of accents, tastes and multilingual, multicultural trivia. His many voices come in handy performing for kids, too.

He even dazzles his new boss (David Koechner) by bonding instantly over a supposed shared love of Blues Traveler and its harmonica-master lead singer, John Popper.

Sarah finds herself tagging along on this stranger’s evening odyssey, donning a neon-smiling plush kitty head for an all night rave as “DJ Meowna” to his DJ Catamice .

“Like DJ Deadmau5?”

“Where do you think he got the idea?”

But as caught up in all this as Sarah professes to be, she doesn’t know this dude. She wakes up in bed with a chameleon tour-guide to Pacific Northwest entertainment, “Matteo” the Argentine ballroom dancer/”Scarface” coke dealer or slam poet “Tim Demint.” And while in character, he never breaks character.

As this upsets her but doesn’t scare her off, any more than a stalker who warns her to “Stay AWAY from him,” Sarah starts probing his mystery, hunting for his secret sadness and taking notes for a possible book as she does.

Yeah, this is sure to work out.

There’s just a touch of antic energy to these early scenes that gives “The Right One” promise. Piling all the incidents and guises this “G” takes on into one night could have been giddy fun. Comedies like this work at a quick and breathless tempo, which would hurtle us and Sarah to the point of “swept away” with mere momentum.

Instead, reality TV producer turned writer-director Ken Mok stops everything cold by having G-for-Godfrey turn off the charm like a switch. This character isn’t remotely engaging or charismatic as himself, so hiding that aspect of him until late in the game is essential, revealing his sad “secret” later in the game a must.

What would Sarah, author of “romance novels for dumb millennials” want with him?

The sparks Thune sets off, in character, with Coleman and with Koechner (in just a couple of scenes) point to this obvious conclusion. The movie only comes to life when our guy is playing other characters.

What’s worse, the squishy relationshippy stuff is strictly a non-starter. Thune as G-Money clicks with Coleman and Thune as unfunny Adam Scott TNG does not.

I think he’s playing the character as accurately as he thinks is called for, but never broadly or energetic enough to make the movie work. When he’s not cute and charming he’s REALLY not cute and charming.

Bad call on somebody’s part. Coleman’s Sarah needed to be more down in the mouth to make her coming-out-of-her-shell journey pay off.

Add the fact that it’s the tamest R-rated romantic comedy in the history of motion pictures to its gloomy pauses and funereal pace and you haven’t got a rom-com on your hands, just a rom-corpse.

MPAA Rating: R for language and sexual references 

Cast: Cleopatra Coleman, Nick Thune, Iliza Shlesinger and David Koechner

Credits: Scripted and directed by Ken Mok. A Lionsgate release.

Running time: 1:31