Joe Biden’s choice of his vice-presidential running mate is imminent. It will be his first “presidential” decision, and is a moment of high consequence for him and his campaign.

And the first 24-to-48 hours are absolutely critical in the formation of a judgment by the public, and the media, as to whether the VP nominee is qualified and the choice can be deemed a success.

What would constitute a winning choice?

First and foremost, given Biden’s age (he will be 78 on Inauguration Day next 20 January), that his VP is seen instantly as capable of becoming president at any moment. So she will have to immediately pass the capability/gravitas test.

Second, that there is fervent acclaim for her ascension across the party, from Bernie Sanders to Jim Clyburn to Nancy Pelosi and Barack Obama; from all the other women who were under consideration; and from every prominent feminist leader, governor, Member of Congress, environmentalist, and union leader in between. The VP choice has to be seen as a unity pick, and one that vindicates Biden’s judgment and cements Biden’s leadership position going into the final ten weeks of the campaign.

Third, that there are no issues of scandal, misdeeds, ethical vulnerabilities, financial improprieties, or salacious episodes that can erupt in the next Twitter cycle. And yes, we will see her tax returns.

Fourth, that there will not emerge past statements or foreign policy gaffes or writings or endorsements that will force the VP nominee to go into a series of defensive press conferences to rationalise her past positions.

Biden’s vetting process is based on the exacting scrutiny he underwent by the Obama vetting team in 2008. They did their job, and this is why the allegations of sexual harassment against Biden that surfaced a couple months ago did not have credence – because the checks on Biden had been done and a colourable case was not there. So, if there was proper vetting of Biden’s choice, there should be very limited vulnerability.

From team Trump in the first 24 hours, the new VP nominee can expect an instant barrage of negative ads and a social media avalanche together with the Fox News echo chamber. (If this has not already been prepared, then the Trump HQ will have committed grievous campaign malpractice.) That assault is just a keystroke away.

Indeed, Trump will not cede even half a news cycle to Biden on his big day: Trump will almost surely have a dramatic announcement on an unrelated issue within hours of Biden’s naming his VP, all designed to change the topic. In 2008, John McCain named Sarah Palin as his VP the morning after Obama’s superb acceptance speech in Denver. It immediately robbed Obama of some momentum coming off his historic presidential nomination.

The first 24 hours after naming his VP are a danger zone for Biden. They will go a long way to defining Biden's VP, and how assured she can be as she enters the campaign arena, and how much credit Biden can gain from making his choice. And that can make all the difference as the presidential campaign is properly joined.