Will Kamala Harris make the difference?

You've probably heard a lot in the past three days about Senator Kamala Harris, her background, and the ground-breaking nature of her candidacy for US vice president.

But now that the cheering crowds have logged off and the virtual confetti has been swept away, we're left with a basic question: will Kamala Harris make a difference — on the campaign trial and maybe in the White House — for Joe Biden?

There are three ways to answer that question.

Can she help Biden unseat President Donald Trump? Early evidence suggests Biden's choice of Harris is fairly popular. As the first black woman and first person of Asian descent on a presidential ticket, she might boost Biden's appeal at the margins with black voters, women, and Indian-Americans, though Biden is already popular with the first two groups.

Less tangibly, but perhaps more importantly, Harris' considerable energy and charisma can boost public excitement for a campaign led by the 77-year-old Biden, a man who has been active in US politics for half a century. On the other hand, her record as a San Francisco prosecutor and California attorney general will trouble some voters on the progressive left who want substantial reform of policing across the United States.

All that said, the historical evidence shows that voters don't care very much whose name appears second on the party ticket.

Can she serve as president on a moment's notice? The vice president's most important constitutional role is to become president if the boss can't continue. Gerald Ford (1974), Lyndon Johnson (1963), and Harry Truman (1945) are the most recent examples.

Senator Harris does have executive experience. As California Attorney General, she ran the second largest justice department in the United States, an organization with 5,000 employees.

She was much less successful, however, at the head of her own 2020 presidential campaign, a mysteriously dysfunctional operation that broke down before the first votes were cast in Democratic primaries.

If Biden wins, can she help him govern? When Biden introduced her on Wednesday as his campaign partner, he said he wants Harris to be the "last voice in the room" after other advisors are gone and someone who will "challenge my assumptions if she disagrees."

The prosecutorial precision with which Harris has questioned witnesses during Senate hearings, and her willingness to go after Biden on the debate stage while she was still a presidential candidate, suggest Harris has more than enough toughness and poise to fill that role. Also important: Biden's trust in Harris is boosted by her longstanding friendship with his late son Beau.

Here's a bonus question....

Is Kamala Harris the future of the Democratic Party? Not so fast. Ask a voter enthusiastic about Senator Harris what they like about her, and you're more likely to hear about her personal strengths and professional achievements than about policy positions.

Progressive voters, increasingly important for the future of the Democratic Party, know what Senator Bernie Sanders believes. They know that Senator Elizabeth Warren has "a plan for that," and they associate emerging star Alexandria Ocasio-Cortez with the "Green New Deal."

If Kamala Harris is to become the dominant voice in her party, she'll have to develop a brand that makes it easier for voters to identify her — and easier for rivals to attack her.

Bottom line: Harris has obvious value for Biden as a respected and trusted policy advisor. Her broader political appeal remains untested.