Attack and parry — that’s what most experts expect in the vice presidential debate between Republican Mike Pence and Democrat Tim Kaine.

The duo have multiple responsibilities as they face off: vigorously exploit their opponents’ vulnerabilities on policy and character; deftly defend their presidential candidate from those attacks; and demonstrate that they are suitably qualified to become president if the circumstances demand.

That last responsibility may be the best reason to watch the debate. At age 70, Donald Trump would be the oldest person elected president. The 68-year old Hillary Clinton would be the second oldest, if elected. What we know about their medical histories is limited to what they want us to know.

As well, the debate may give us a glimpse into the possible political futures of Kaine, a U.S. senator from Virginia and Pence, the governor of Indiana.

If nothing else, we will see how they do for 90 minutes in the spotlight before they fade back into the shadows of the campaign.