What if Biden stumbles? Democrats need a strong alternative candidate with stakes so high.

Conventional wisdom says that it is too late for a strong Democrat to challenge President Joe Biden for the 2024 presidential nomination, and that any such challenge would hurt Biden and let the GOP win the White House.

That conventional wisdom is wrong.

Pundits and scholars have agreed for decades that a strong challenge to an incumbent president is always bad for reelection. Democratic Sen. Ted Kennedy's challenge in 1980 made President Jimmy Carter look weak. Republican Pat Buchanan in 1992 made President George H.W. Bush bleed in New Hampshire.

One-term presidencies are rare, but they seem to go with intraparty turmoil. Meanwhile, successful reelections – like Ronald Reagan 1984, Bill Clinton 1996, George W. Bush 2004 and Barack Obama in 2012 – come with easy paths to renomination.

It is the fear of damaging Biden in the primaries, and then Biden losing to former President Donald Trump, that has kept strong Democrats from the challenge.

How a challenger to Biden can help Democrats

How can someone run against Biden and not hurt him? Two ways.

First, the challenger needs to promise fellow Democrats from the start that they won't attack Biden on policy or on personal issues like his age or his son's legal problems. They just think they would make a better president than Biden – and they'll explain why.

Second, and equally important, they will campaign with a blank calendar for July to November of 2024. They'll pledge that if Biden wins the nomination, they will campaign or fundraise for him every day until the election.

Biden will not look strong if he takes the nomination by beating conspiracy theorist gadfly Robert F. Kennedy Jr. He will benefit from a strong challenge that shows he still has the old fire in his belly.

But isn’t it too late?  There’s not enough time to raise the money or put a staff together in the early states, right?

The speed with which social media moves ideas, and the rapidity with which the internet allows fundraising to happen, means that someone, say a popular Democratic governor, could announce in September that they are running and raise millions in a few days. In 2016, Trump ran a lean campaign that relied heavily on social media. An insurgent Democrat could do the same.

2024 election: Trump vs. Biden (again) is bad for America. We're ready with an alternative.

Biden is perhaps the most vulnerable incumbent we’ve ever seen, within his own party. Some surveys show a majority of Democrats want someone else to run. They’ll almost all vote for him against any Republican, but they openly wish that someone better, and yes, someone younger, were running.

Democrats like Biden, and most say he’s done a pretty good job. Democrats are also eternally grateful to him for beating Trump in 2020. But they don’t love Biden. He doesn’t have the charisma or energy of a Bill Clinton or Barack Obama. And most of them wish they had another option.

And they could and should be given one.

Bad debate could sink Biden before general election

There is a darker prospect that should make every Democrat want a challenger to Biden. Most of the attacks on Biden as senile are unfair, snippets of videos that mistake fumbling with words for dementia. But if you haven’t seen at least one mildly troubling video of Biden being confused, you haven’t been paying attention. And Republicans will launch devastating ads showing Biden at his worst as soon as he has the nomination sewed up.

Now, put Biden on a debate stage with Florida Gov. Ron DeSantis, Trump or any other Republican. And let’s suppose he has a bad night. Or let’s suppose there really is some decline, and he’s not as good as he was even in 2020.

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Ask yourselves, Democrats: Would you rather find that out in January when Biden debates a Democrat, and you could still choose an alternative Democrat, or find it out a few weeks before the election, when a bad debate night could turn a close election into a rout?

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Biden will not be a sore loser if he gets beat in the primaries, particularly by someone who has been praising him constantly. Biden will be disappointed, and then he’ll be the loyal soldier that he was for Obama. He’s a Democrat at the molecular level.

So, governors of Pennsylvania, Michigan and elsewhere, and certain Cabinet secretaries and senators, it’s time to look in the mirror and ask yourself – do you see a president?

And then see about doing some trips to New Hampshire and South Carolina, maybe Nevada. You know, just to test the waters.

There’s still time, and there is still a chance.

Jeremy D. Mayer, an associate professor of policy and government at George Mason University, is the co-author of the forthcoming "The Changing Political South."

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This article originally appeared on USA TODAY: Why America needs a strong Democrat to challenge Biden for president