The big decision for Biden looms - and this time it matters

Joe Biden is expected to announce his running mate within the next 48 hours. Credit: PA

Joe Biden has made up his mind. He has chosen his running mate and is set to announce it within the next 48 hours, possibly later today.

And it matters vastly more than usual.  

If he wins in November - which the polls predict - then Biden will be (by some distance) the oldest President ever elected.  

In fact, he would be older at the start of his presidency than Ronald Reagan was at the end of his two terms.

For that reason, from day one, Biden's running mate will be seen as a possible president.

If Biden doesn't survive his first term, or steps aside for health reasons, then the person he is about to pick as his partner in the White House will become America's 47th President.

No wonder the country is watching the choice so closely.

We do not know who he will pick. It is the best kept secret in American politics right now. (Though dozens of journalists are tracking the movement of private jets into Delaware to try and get the scoop).

Kamala Harris has been mooted as a possible running mate. Credit: AP

But we do know for sure that it will be a woman. Biden has long promised his party that there will be gender diversity on the ticket.  

That is in no small part because of disappointment among many Democrats during the primaries earlier this year. 

The party had lined up a wonderfully diverse and fresh field of candidates to select the presidential nominee...only for party voters to go for an old white man who's been around Washington for fifty years.

There is still suspense over the question of whether Biden will choose a woman of colour, which would break a glass ceiling in the world of presidential politics.

Elizabeth Warren may be a potential candidate. Credit: AP

Two black women are widely considered front runners: Senator Kamala Harris (her father was Jamaican; her mother was from India), and Susan Rice, who was Obama's National Security Adviser.

But some within the party are pushing the case for a white women, notably Elizabeth Warren, the progressive Senator from Massachusetts, and Gretchen Whitmer, the Governor of the key Midwestern battleground state of Michigan.

US political analysts always argue about whether a VP pick makes a difference. Does it actually persuade any undecided voters to change their mind? There is scant empirical evidence (though perhaps LBJ helped Kennedy win the White House in 1960 by securing Texas).

This time the decision could be truly significant. Biden is already looking frail. Trump has regularly suggested that his rival is in cognitive decline.

So whoever become Biden's running mate needs to be ready not just for the most raucous and volcanic election campaign for decades, but also to be commander-in-chief.

Americans need to look at Biden's VP choice this week and be persuaded that she has the stature of a future President.