Time was when getting caught in a malicious lie about a rival would have ended an American politician’s career. We no longer live that way. Just the other day, Donald Trump unleashed a torrent of falsehoods attacking President Joe Biden that would have shamed a carnival barker.

Speaking to a rally in South Dakota, Trump delivered a series of mocking claims, beginning with the allegation that the administration was using made-up jobs numbers: If you ask Trump, only 2.1 million jobs have been created during the president’s 30 months in office. The actual statistics show somewhere over 13 million jobs — along with near-record growth in GDP (Gross Domestic Product) during the recovery from the 2020 COVID slump.

Then Trump got personal. “He makes up these stories, like there’s a picture of a fighter jet ... [mocking] ‘I used to be a fighter jet pilot.’ Then there’s a picture of a truck. ‘I used to drive a truck.’ The worst is, did you ever see his golf swing? He said he’s a 6-handicap! A 6-handicap is a good golfer. This guy can’t hit a ball ... I think that’s the greatest lie of all, if you want to know the truth.”

Trump shakes his head in feigned disbelief as the crowd laughs and applauds. (Never mind that there’s a best-selling book by veteran sportswriter Rick Reilly called “Commander in Cheat: How Golf Explains Trump,” describing how he races down fairways in his golf cart, kicks opponents’ balls into ponds, drops his own onto the green, etc. Filled with interviews of golf pros and caddies, it’s actually quite funny.)

So is Trump’s performance, or it would be if you didn’t know — South Dakota isn’t exactly a golfing hotbed — that every single word of it is a malicious lie. Biden has never claimed to be a truck driver or a fighter pilot. Don’t you think you’d have heard?

Biden has mostly made self-deprecating jokes about his golf game, commenting that “the course record remains intact” after his initial outing as president. Back in 2018, he carried a USGA handicap of 6.7, according to Golf News Net, which is pretty good — no surprise, as Biden was an accomplished athlete as a young man. But he’s never boasted about it.

Anyway, who cares? As a politician, Trump himself is treated by audiences and reporters alike as a stand-up comic, which would be fine if he stuck to stage performances. Alas, polls show that millions of gullible Americans believe even the most absurd of his inventions. Deep-thinking pundits are writing columns about Biden’s great unpopularity, which reality-oriented blogger Kevin Drum shows is largely a function of false memories.

Biden’s popularity is on par with past presidents

I like Drum because he’s an engineer by training who lives in Orange County, California, and he’s congenitally immune to inside-the-Beltway conventional wisdom. Recently he posted a graph comparing the favorability ratings of the last several presidents at the equivalent points in their respective administrations. It turns out that they all hovered in the 40s. It comes with the territory. Biden’s in no worse shape politically than Clinton, Obama or Trump.

Only George W. Bush, thanks to the strong patriotic surge in response to the 9/11 terrorist attacks, was in better shape. However, Dubya’s disastrous second term drove his approval down to 24% by 2008.

So, no, Biden isn’t deeply unpopular with the public, and certainly not in comparison with Trump, whose negatives are markedly worse even in Fox News surveys. That said, polls mean very little at this point in the election cycle and have largely failed to predict the results in any of the last several national contests.

Remember the vaunted “red wave” in 2022? Never happened. People don’t answer their phones anymore unless they know who’s calling. The whole business of public opinion polling is an increasingly shaky enterprise.

I suspect it’s the same with the Fox News-generated Hunter Biden saga. Supposedly, a majority of Americans believe Joe Biden has violated the law in his dealings with his wayward son. It’s not against the law to work for a foreign corporation, nor to drop Daddy’s name in business meetings.

If it were, there wouldn’t be a Trump in-law walking around free, much less cashing humongous checks from Saudi Arabia.

Doting father that he is, I quite doubt that Biden fills out Hunter’s IRS form 1040. Nor that after decades in public life with no sign of financial impropriety, he suddenly got greedy in his 70s. However, the Fox News imagineers appear to have persuaded millions of viewers that with all the manure they’ve shoveled, there must be a pony.

Gullible cynicism regarding politicians is always tempting. But if they go ahead and impeach the president, they’d damned well better produce that pony.

Gene Lyons is a National Magazine Award winner and co-author of “The Hunting of the President.”