Editor’s Note: Joe Lockhart is a CNN political analyst. He was the White House press secretary from 1998-2000 in President Bill Clinton’s administration. He co-hosts the podcast “Words Matter.” The opinions expressed in this commentary are his own. View more opinion at CNN.

CNN  — 

Joe Biden has promised to announce his choice for vice president in the coming days. While political insiders and members of the media have obsessed over every possible contender, the announcement will likely be forgotten within days as focus will revert to the pandemic and the candidates at the top of the ticket.

Joe Lockhart

The last time a VP pick was instrumental to a race was 1960, when Texas Democrat Lyndon B. Johnson helped put John F. Kennedy over the top by attracting votes from the South. There have been plenty of strong candidates and incredibly flawed VP picks since then, but none have helped determine the outcome of the presidential race. Put another way, John McCain didn’t lose because he picked Sarah Palin in 2008, but it sure didn’t help.

All of this is not to say the VP pick is not important. The decision – once a means of finding ideological or regional balance – is increasingly a test of the candidate’s judgment and an early indication of the kind of administration he intends to run.

Bill Clinton, for example, was widely expected to choose someone from the more liberal wing of the Democratic party and not another son of the South. But by choosing Al Gore, he made a broader and bolder statement; this campaign was about generational change and a new style of leadership. Both Clinton and Gore were younger men in their mid-40s who brought more physical energy to the race than George H. W. Bush, then in his late 60s. The contrast fueled the narrative that America needed new, younger leadership.

More importantly, Clinton and Gore were comfortable with each other and shared the same basic world view. The same was true for Barack Obama and Biden and, for better or worse, Richard Nixon and Spiro Agnew.

Ultimately, the success of a VP pick comes down to these two factors: whether the two running mates share a genuine and comfortable partnership, and whether the VP reinforces the broad message about how the presidential candidate intends to govern.

So, what is Biden going to do? He has already made the kind of statement Bill Clinton did by picking Gore – making generational change a centerpiece of the campaign. By committing to pick a woman early in the campaign, Biden signaled his intention to break the glass ceiling. Women are the key to Biden’s election success, particularly Black women. This was an important message from the beginning, helping to blunt any unease within the Democratic party that Biden was just another old guy in the party.

Now the only question is: which woman? Judging from his experience with Obama, the former vice president will want to pick someone he’s comfortable with – someone he knows and trusts. Vetting the VP choice is one of the most consequential jobs of a fledgling presidential campaign. If the first rule of VP picks is to do no harm, the second rule is this: absolutely no surprises. Biden will want to avoid any unwelcome revelations such as we’ve seen in the past – like Palin’s much-mocked ignorance about international affairs and Geraldine Ferraro’s husband’s finances becoming a flash point when she announced he would not be releasing his tax returns.

Getting the vetting right is an important test of competency. And that’s especially important in this election cycle. Biden is running as the candidate who won’t make the mistakes the Trump administration made from day one. Messing up the VP would seriously undermine the whole competency narrative.

It should be said no contender is perfect or baggage-free. But don’t mistake the public criticisms of various VP choices – from Kamala Harris’ supposed ambition to Rep. Karen Bass’s past comments about Scientology – as immediately disqualifying. More often than not, that information will be floated out by the campaign to judge the public’s reaction before a decision is made. Any new information reported after the pick is announced takes on much more importance and signals the campaign failed in fully vetting the pick.

How the new VP candidate is rolled out is also an important test. Even if you believe my theory that the VP pick only matters for a few days, those few days are very important. Developing a showcase announcement tour that highlights the strengths of the candidate and how they both complement and reinforce each other is both a messaging challenge and a cultural test of how well the running mates and their respective staff members can work together. McCain and his staff had significant problems dealing with Palin and her staff. On the flip side, the bus tour out of the Democratic convention in 1992 cemented the generational change both Clinton and Gore were aiming to convey.

It’s age-old wisdom that the vice president also has to be the attack dog, but that has been less true in recent years and mostly irrelevant this year. The main issue in this campaign is Trump. Biden’s pick will help serve as a contrast to the incumbent and demonstrate the ability for the Biden administration to hit the ground running on day one.

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    Biden’s vice president will, of course, need to appeal to core Democratic constituencies, minority communities and women. Biden has a wealth of choices on that front and it’s hard to see, as long as the vetting is done properly, how he could go wrong.

    McCain shocked the political elite by picking Palin as a way of shaking up the race. Walter Mondale did the same by picking Ferraro in 1984. And Clinton surprised the country by picking another Southerner. For Biden, the task is different. Biden’s challenge is just the opposite. His pick needs to be designed to maintain the structure of the race rather than changing the dynamic. The very last thing he needs now is to spring a surprise on all of us.