Nearly one-third of Vice Presidents go on to later become President.

Joe Biden has made a cautious and deliberate choice which could also prove historic if the California senator ends up succeeding him in the White House.

Harris is not only the first Black woman on a presidential major-party ticket, but also the first Asian-American. The Trump campaign is already on the attack, claiming Harris is an opportunist who will push an ageing Biden to cave in to the radical left. In one example, Trump and his allies have alluded to Harris confronting Biden on a primary debate stage over his role in undermining school integration in the 1970s as a first-term senator. Yet this meandering line of attack merely shows the difficulty the Republican campaign will have in landing a blow against a more moderate opponent, which Harris undoubtedly is, as opposed to, say, a Bernie Sanders.

Ironically, Harris has also faced criticism from voices on the left who claim she actually breaks too few barriers: as a former prosecutor and attorney general, she has distanced herself from the defund-the-police demands that emerged in the wake of the murder of George Floyd.

“I know it can’t be a political decision,” Biden himself has said of the pick. “It has to be a governing decision. We’re going to inherit a nation in crisis, a nation divided, and a world in disarray. We won’t have a minute to waste. That’s what led me to Kamala Harris.”

Moving the needle

The bigger question is how much of an impact Harris will have on the outcome of the presidential race. Black turnout is critical for the Democrats. Take the example of swing-state Wisconsin in 2016. Black voter turnout there fell by 88,000 from four years earlier, while Democrats lost the state by fewer than 23,000 votes. One analyst is predicting an extremely high turnout from Black voters this fall now that one of the Democratic Party’s most loyal constituencies—Black women—see themselves reflected on the ticket. Nevertheless, a recent poll testing Biden’s popularity alongside 12 potential running mates found no statistical difference on account of Harris.

And that’s the historical pattern.

Vice-presidents may not often move votes. The more important statistic is that they occasionally move into the White House: Nearly one-third of those who’ve held the role went on to later become president. And should the Biden-Harris campaign be successful this year, America’s next VP really could make history.