Jeff Greenfield is a five-time Emmy-winning network television analyst and author.

On paper, it should not be all that hard for Joe Biden to make a forceful case at tonight’s debate.

He can make the “let’s get real” argument that sweeping progressive New Deal and Great Society policies have been enacted when Democrats held landslide majorities in Congress; that without such power, even less ambitious efforts, like the Affordable Care Act, face serious headwinds and can come at a political price.


He can argue that a health care proposal that takes away private plans is simply asking too much of a populace whose distrust of government is at record levels. He can adopt a version of Bill Clinton’s 1992 method, showing that Democrats win “when people believe they can trust us with their safety and their money.”

There’s one problem, though: Debates do not happen on paper. A candidate and staff may have artfully constructed strategies and arguments, but without the ability to summon them in real time, they are useless if not dangerous. (Recall Rick Perry in 2012, unable to remember which three federal agencies he was going to abolish, or Marco Rubio in 2016 robotically reciting an indictment against Barack Obama even as Chris Christie was ridiculing him for that very soundbite.) In the debates thus far, and in his climate change town hall, Biden has run into more than his share of awkward moments: He was unprepared to defend himself against a pointed critique of his work with segregationists, unprepared to explain a fundraiser hosted by a fossil fuel investor, and frequently unable to complete a thought or to respond directly to a question.

At first glance this is odd; why, after nearly half a century in public life, after decades spent in debates on the Senate floor and in committee, is Biden struggling to deliver a forceful, coherent performance? The surprising answer is, he has actually not had that much experience in televised debates with multiple candidates. Indeed, his best performances have come in his two vice presidential debates; one-on-one contests with a single adversary whose arguments were familiar, and with plenty of speaking time to flex his storytelling muscles. Until this year, he has never found himself in a crowded debate as a front-runner, where he is the clear target of opportunity. Thus far, he has seemed unprepared for the challenge.

When Biden first ran for president more than 30 years ago, a combination of missteps forced him out of the race a year before the campaign began. But he did participate in early debates, and in one of them he committed a grievous error. He had made a hit of quoting British Labor leader Neil Kinnock’s biographical reflection—(“Why am I the first Kinnock in a thousand generations to be able to get to university?” Why is [my wife] Glenys the first woman in her family in a thousand generations to be able to get to university?”) and comparing it to his own humble beginnings. But in an August 23rd debate in Iowa, Biden never referred to Kinnock—and the charge of plagiarism helped drive him from the race.

In 2008, he was out of the race a day after the Iowa caucuses; and through the 2007 campaign, he was a marginal figure, with a poll rating roughly equal to former Cleveland Mayor Dennis Kucinich. No other candidate bothered to criticize him—the 2007 debates were models of civility in any event—and Biden’s comments, limited by the sheer number of candidates, focused on his work on the 1994 crime bill, his decades of experience and a view of Iraq that minimized his support for the invasion—a portrait at serious odds with the record, as this RealClearPolitics piece illustrates. The political world took little note nor long remembered what he said, because he was a footnote in the Obama-Clinton-Edwards battle.

The vice presidential debates were a different story. In his 2008 faceoff with Sarah Palin, Biden treated his cognitively challenged rival with respect, avoiding any direct attack on the governor, while aiming his fire at the GOP presidential candidate, John McCain, in measured terms.

“It was two Mondays ago John McCain said at 9 o’clock in the morning that the fundamentals of the economy were strong. Two weeks before that, he said George—we’ve made great economic progress under George Bush’s policies. Nine o’clock, the economy was strong. Eleven o’clock that same day, two Mondays ago, John McCain said that we have an economic crisis. That doesn’t make John McCain a bad guy, but it does point out he’s out of touch.” It was a workmanlike presentation in tone and substance.

You can get a better sense of Biden’s debate style by looking at the 2012 vice presidential debate with Paul Ryan. Coming just days after Obama’s zombie-like performance against Mitt Romney, the Full Biden was on display.

It was, as the Guardian wrote, “A high-energy performance—part angry bar-room debater, part condescending elder uncle, part comic mime artist—[that] frequently seemed to leave Paul Ryan overwhelmed.” There were frequent interjections of laughter, mocking smiles, exaggerated shakes of the head, and more than one assertion that his opponent was offering “a bunch of malarkey.”

More substantively, Biden managed to remind the audience of what the members of the Obama administration had encountered on Day One, and to contrast their actions with Romney’s self-inflicted wounds. “We immediately went out and rescued General Motors,” Biden said. “We went ahead and made sure that we cut taxes for the middle class. And in addition to that, when that—and when that occurred, what did Romney do? Romney said, no, let Detroit go bankrupt. We moved in and helped people refinance their homes. Governor Romney said, no, let foreclosures hit the bottom.

“But it shouldn’t be surprising for a guy who says 47 percent of the American people are unwilling to take responsibility for their own lives. My friend recently, in a speech in Washington, said 30 percent of the American people are takers. These people are my mom and dad, the people I grew up with, my neighbors.”

Biden did effective work here, especially in rallying Democrats disheartened by Obama’s poor debate. But there’s a catch. This was a two-person debate with a flexible format permitting time to answer questions in some detail and a skilled moderator (Martha Raddatz) who knew how to guide a conversation. And since Biden was debating a Republican adversary, he was free to employ sarcasm, ridicule and an eyeball rolling response to Ryan.

Thursday’s debate is a 10-person affair, with a minivan-sized group of fellow Democrats. Biden’s scorched-earth approach to Ryan would not be greeted warmly by a Democratic electorate still considering any of the 10 debaters as a potential rival to Donald Trump. And this time, unlike the 2008 race, Biden will be an obvious target. Each of Biden’s rivals are aware that their fortunes depend on knocking the front-runner off his stride, and they may take cues from what has already happened. Kamala Harris effectively knocked Biden back on his heels in a June debate when she took him on for opposing school busing. Biden was better at July’s CNN debate, but at the town hall on climate change, after a single well-prepared hostile questioner demanded to know why Biden was attending a fundraiser hosted by a fossil fuel investor, Biden’s distinction between an “investor” and an “executive” was less than decisive. Further, there were several nonhostile questions where Biden seemed to lose his train of thought, pivoting from one assertion to another.

For some, the explanation was age. But it may just be that Biden’s strengths as a storyteller and a conversationalist simply do not play well in the rapid-fire, truncated Q&A format of a primary debate. Biden is best when a format allows for the “Scranton Joe” anecdotes, the humorous asides, slips of the tongue that can be waved aside, the one-on-one interchanges with a single adversary. Biden will have none of those advantages tonight.

All of which raises another question: How much do debating skills matter? They can sometimes undermine a campaign, as with Rick Perry and Marco Rubio, and sometimes sustain them, as with Newt Gingrich through much of 2012. We have also seen in the past that (to paraphrase financial company ads) poor past performance is no guarantee of future results. Ronald Reagan had a dreadful first debate in 1984 that raised questions about his faculties; he went on to win 49 states. Obama was missing in action in 2012’s first clash with Romney and won a reasonably comfortable reelection. And however uncertain Biden was in that first debate and at the town hall, most polling has him remaining atop the Democratic field.

Still, the past also teaches that the front-runner perch at this stage of a campaign is less than secure. (Just ask Ed Muskie or Howard Dean or Rudy Giuliani or Hillary Clinton.) This coming debate is Biden’s best chance to refute the questions about age and capacity … or to make them bigger dangers to his nomination.