Opinion by Dean Obeidallah

(CNN) -- Joe Biden on Saturday utterly devastated one of President Donald Trump's most repeated attack lines against the former Vice President. And the irony is Fox News helped him do it.

On the day that Trump was at his ritzy, exclusive country club in Bedminster, New Jersey, that reportedly has a $350,000 admission fee, Biden did what so many typical Americans do for recreation: He rode a bike.

The former vice president, who was wearing a mask, was accompanied on his bicycle ride by a few others on the streets of his home state of Delaware when they were approached by Fox News' Peter Doocy. The Fox reporter yelled at the bike-riding Biden: "Mr. Vice President have you picked a running mate yet?" to which Biden responded, "Yeah I have." Doocy then followed up, "You have? Who is it?" to which Biden jokingly replied, "You!"

That exchange not only aired on Fox News, it went viral on social media. And then almost on cue Saturday afternoon, around the same time Biden was on his bicycle, Trump tweeted out from the posh confines of his country club one of his go-to attack lines against the former VP, calling him "Sleepy Joe Biden."

The irony was delicious. There's Biden briskly riding a bicycle while Trump is at his private country club, where the only exercise he seems to get is getting in and out of his golf cart. Yet Trump is calling Biden "Sleepy." Sometimes comedy writes itself. But in this case Twitter helped as the hashtag "Trump Can't ride a Bike" got traction online, with one anti-Trumper juxtaposing video footage of Biden riding his bicycle with Trump struggling to walk down a ramp after delivering the commencement address in June at West Point.

It's certainly true that Trump has made Biden's stamina -- as well as the former vice president's mental capacity -- an issue in this campaign. Voters don't necessarily agree: a poll in early July found that 52% of voters believe Biden has both the mental and physical stamina to be president versus only 45% for Trump. But here's an idea that might convince even higher numbers. Instead of a fourth debate that Trump's team wants, why not hold a good old-fashioned bicycle race between the two?! Trump loves ratings and this would no doubt attract millions! I can't even imagine how many will tune in just to see if Trump can even balance on a bicycle, let alone ride one.

What is also striking about this "riding with Biden" image is that it stands out in glaring contrast to another Democratic presidential nominee's moment of recreation that backfired. That happened in August 2004 when Democrat John Kerry, who was taking on incumbent President George W. Bush, was photographed windsurfing off the coast of Nantucket. Reportedly the photo op was intended "to combat Kerry's image as a stiff-jawed ivy-leaguer." Not only did late night hosts at the time like David Letterman and Jay Leno mock Kerry for the image, conservative blogs slammed Kerry for his "elitist" hobby. It got worse as the Bush campaign used the image in a campaign ad accusing Kerry shifting positions with the "wind.

(Kerry was an avid cyclist too, but his custom-made bikes and exotic riding destinations didn't send the same message as Biden's "everyman" bike ride.)

An even worse image for a Democratic presidential nominee -- probably the worst ever photo op for a modern day presidential candidate -- occurred in September 1988 when Michael Dukakis, in an effort to bolster his credibility to be commander in chief, donned a military helmet and rode in a M1A1 Abrams Main Battle Tank. Even the campaign reporters covering Dukakis at the time couldn't contain their laughter upon seeing the unfortunate image that made the candidate appear desperate and goofy. His opponent, George H. W. Bush, later utilized this image of Dukakis in ads attacking the Democratic nominee as being weak on defense.

Compare those images to Biden on the bicycle. There's no indication that this was a contrived photo op. It appears to be simply be Biden being Biden. He went out for a bike ride and Fox News happened to capture it. It's the same as Trump just being Trump over the weekend where he palled around with his rich friends at his private country club and then abruptly ended a press conference after being caught lying by a reporter.

The contrast for voters this November could not be starker.