Judging by their campaign ads, the leading Republican candidates for president appear to agree on one thing: They’re strongly pro-spark.

Images of factory workers producing sparks — fountains of them, rivers of them, random bursts of them — have become the visual cliche of this year’s crop of GOP ads and videos. They’re almost as common as American flags fluttering in backlighted beauty shots; they’re surely as numerous as those sunny pictures of farm machines harvesting amber waves of grain and of American soldiers marching in precision.

Newt Gingrich, the current front-runner, lets the sparks fly early and often in his first TV ad in Iowa. “Working together, I know I can rebuild America,” he says as two hard-hatted men throw twin sprays of sparks to a factory floor.

Got that? Sparks = jobs.

Seconds later in the Gingrich ad, there’s a shot of a foundry, sparks aflying.

Not to be outdone, Rick Perry and Mitt Romney lay on the sparkle, or at least the sparks, too.

Romney packs not one but two sparkly images into a one-minute ad called “Believe in America. ” The first — a clip of a worker generating sparks while grinding a metal object — is timed to appear on the word “jobs” as Romney, in voiceover, says, “I’m going to get rid of Obamacare. It’s killing jobs.” A few seconds later, a spark-throwing, metal-cutting machine appears, just after Romney promises to make America “a jobs-creating machine.”

Perry’s ad wizards liked the spark thing so much that they put it in two ads. “It’s time to get America working again,” the Texas governor says in one, as the camera cuts to disembodied hands operating a machine that, yes, produces hopping and dancing sparks. The second, in which Perry talks about boosting the domestic energy industry (oddly enough, while making a speech at a Pennsylvania steel mill) works in some sparks as the music swells. “Let’s get back to what we know works,” Perry says, “and that’s to get America working again.”

Why sparks?

On a basic level, sparks are a good visual for TV and Web video, says William Benoit, a communications studies professor at Ohio University. They’re as lively as fireworks, if not quite as colorful.

“Our attention is attracted by bright things and, because we were once hunters, we are attracted to movement,” Benoit says. “So, this is a shorthand visual for jobs, with the bonus of attracting the viewers’ attention because this video includes movement and bright lights.”

Another bonus: It doesn’t take much thought or effort to understand what’s happening when the sparks start flying. The image can flash by in just a second or two and be easily grasped. “Ads are short, and they need to be easily and rapidly understood,” Benoit says. Admakers want “as much easily interpretable information” as possible.

And in this context, sparks have potent political symbolism, connecting a candidate to an image that suggests hard work and American industrial might. No matter that most voters aren’t welders or factory workers, or that manufacturing jobs have been declining as a percentage of the American workforce for decades. Voters can still relate to something that signifies “blue collar,” says Travis Ridout, an associate professor of political science at Washington State University.

Ridout says the sparks suggest that the candidates are trying to appeal to men, as the stereotypical factory worker who runs a spark-producing device is likely to be male (not to mention that men have been seeing sparks thrown in the background of pickup truck ads for years).

He also suggests that one potential target of the ads are “Reagan Democrats” — white, working-class voters from northern states such as Iowa who might be enticed to vote for a Republican.

In any case, sparks surely beat other kinds of images that could have been used to suggest “work” or “jobs.” Don’t expect anyone to run an upbeat ad showing an office full of investment bankers anytime soon.