Here’s quiz for the eve of this election — can you summarize in one sentence Hillary Clinton’s prime justification for being elected president Tuesday?

Me neither.

If pressed, many will say, “Trump is unfit for office and endangers America’s future.” Others will echo Barack Obama’s praise for his intended successor: “She’s the most experienced and office-ready candidate in our nation’s history.’’

“The other guy’s lousy and my résumé’s long” makes for just about the worst campaign button in history.

What does Clinton have to say on her own behalf? Yes, she would be the first female president, and that glass ceiling may be broken on Nov. 8. But then again, Carly Fiorina or Elizabeth Warren had a potential claim on that distinction.

Her inability or unwillingness to distill a message into language both memorable and personal has mattered throughout this campaign. It’s the reason she ends her run for the top job in a defensive crouch, scaremongering (with justification) about her opponent, and ducking the latest anonymous mud-flinging from the New York field office of the FBI.

[Opinion: Hillary, Bad Karma and the Fate of Democracy]

Say this for Donald J. Trump: For all the pundit hours spent wondering why he can’t stay “on message,” his insults, vendettas and mockery have never obscured the core justification for his candidacy.

America, according to Trump, is a mess and he alone can fix it. And every Trump supporter at every campaign rally knows and believes that message.

Democrats have responded to this inspiration gap with dogged fundraising and a return to the Obama campaign’s sophisticated registration and get-out-the-vote mechanisms. That may win the office, but Clinton could be handicapped in governing by the ardor gap among her own supporters.

If she triumphs rather than wins by an inch, she’ll have those 50 million voters who have registered since 2008 to thank — many of them Hispanics enraged by Trump’s candidacy from Day One. And as the Pew Research Center notes, the non-Hispanic white share of the electorate has fallen from 71 percent to 69 percent in just four years. So, yes, the dead may help elect Clinton — by not being available to vote against her.

In Clinton’s defense, two decades’ worth of Republican calumnies left her with limited choices for a campaign persona. The hesitancy to emphasize her professional experience or her groundbreaking perspective as a mother running for president is understandable. No one loves an insider, and the mother card appears diminishing to someone who (whisper it) is a feminist.

Yet when was the last time — or the first time — Clinton brought forth a strong and concise case for the Democrats’ stewardship of the economy? The record months of job growth since the recession? The evident levels of heightened prosperity in cities such as Atlanta, Denver and Phoenix, to name three urban centers in purple or red states she may win?

[Opinion: Time for Democrats to Build a Bigger Tent]

Imagine a campaign where a confident Clinton could defend the Affordable Care Act in the context of her failure to get reform in the early 1990s? Such humility — and recognition of Obama’s signature domestic policy achievement — would have allowed her to pivot to a stronger defense of health care coverage.

Instead, she spent a considerable amount of time at the town hall presidential debate arguing against a Republican repeal of Obamacare.

Noting that lifetime caps and child coverage to 26 are endangered by repeal, Clinton essentially re-litigated the 2010 law, apologizing for premium increases instead of offering an argument for strengthening and expanding Obamacare — as is her intention.

It’s no wonder that comedian Bill Maher, an ardent Clinton supporter, just last week lamented that she “campaigns like a hospice nurse.”

It’s not like the campaign hasn’t had a lot of time see this flaw and make adjustments.

At her campaign launch on Roosevelt Island in New York in June 2015, Clinton recalled and praised Franklin Roosevelt’s “Four Freedoms” without actually defining them. FDR, the first mass media political genius, distilled them into four simple sentences amounting to 12 words.

Freedom of speech. Freedom of worship. Freedom from want. Freedom from fear.

Hillary Clinton should know them well — they are etched on the FDR memorial her husband opened during his presidency, right next to the path she anonymously jogged on some mornings as first lady.

[Opinion: Clinton’s Natural Inclinations Fit the Nation’s Mood]

Instead, Clinton offered to wage “four fights” so anodyne I suspect not one attendee can recall them now. (The first was a radical and unique pledge to “make the economy work for everyday Americans.”)

Clinton’s kickoff speech did contain poignant memories of her mother Dorothy, and she has repeatedly made reference to her late mom as something of an arms-length context for her own historic candidacy. Wearing white at major speeches is a subliminal nod to the suffragettes that resonates with feminist historians and just about no one else.

A long time ago in a political world that amounts to a galaxy far, far away, journalist Roger Mudd sat down with a man considered destined for the Oval Office. A year before the 1980 general election, Mudd asked a simple question of Sen. Ted Kennedy: “Why do you want to be president?”

Kennedy’s hesitant, discursive answer played into the narrative that he was a reluctant warrior for the White House, thrust into a role meant for his older brothers. It has passed into legend as a moment that crippled his campaign even before it began.

Today, we don’t have broadcast networks pre-empting prime-time entertainment programming for sober sit-downs with politicians introduced by Aaron Copland’s majestic “Appalachian Spring.”

Instead, one of the era’s prime-time stars is the last thing standing in the way of Hillary Clinton becoming president.

Lucky for Clinton that no one stood up at that town hall with the same simple query that derailed Kennedy.

Come Tuesday night, let’s hope she comes up with a clear explanation to an anxious nation of her goals as president, preferably short enough to one day be chiseled upon a wall of granite.

Ellis is chief content officer of CQ Roll Call.