WASHINGTON When Mike Pence and Kamala Harris take the debate stage Wednesday evening, Americans could potentially be watching both the 46th and 48th presidents of the United States.

The ages of Donald Trump , 74 who is the 45th president and Democratic challenger Joe Biden , 77, already put additional scrutiny on their running mates. Add in the coronavirus pandemic and Trumps recent positive diagnosis for the illness, and the undercard matchup suddenly becomes even more relevant.

You realize that due to how old and ill Donald Trump is, that Mike Pence could be president next week, said Rice University historian Douglas Brinkley. Conversely, Joe Biden would be the oldest president ever elected, so people will be looking at Kamala Harris.

Vice presidential debates have never attracted as much attention as those between the presidential nominees. The faceoff between Pence, then the governor of Indiana, and Virginia Sen. Tim Kaine (D) in 2016 was not particularly memorable. Nor was the one between then-Vice President Biden and then-Wisconsin Rep. Paul Ryan (R) in 2012. The debate between Republican Dick Cheney and Democrat Joe Lieberman in 2000 was more of a quiet conversation.

In none of these and other recent vice presidential debates, however, was there a foreseeable possibility that either of the participants would become president in the near future.

But Wednesday night, Pence will take the stage as Trump remains in the residence at the White House, battling a virus that is particularly deadly to the elderly and the obese.

While the White House physician has been reporting that Trump is doing well and improving, he could easily deteriorate, forcing him to transfer power to Pence if he requires sedation. In a worst-case scenario but one that has happened to 5% of patients over 70 and that nearly happened to a much younger Boris Johnson, the British prime minister the disease could prove fatal.

Brinkley said the only previous occasion he can recall where a presidential nominees health was a serious concern during an election was in 1956, the year after President Dwight Eisenhower had suffered a heart attack in his first term.

Some people were wondering if Richard Nixon was cut out to be president, Brinkley said of Eisenhowers vice president, who would a dozen years later win the White House himself.

Bidens age, meanwhile, will likely push Harris into a different role than that of the traditional running mate. Rather than focus primarily on attacking Trump and Pence, Harris will have to show her ability to step into the top job if necessary, Brinkley said.

Should he win, Bidens age could also mean that he might choose not to run for a second term making Harris performance at the debate a potential early audition for the Democratic primary in 2024.

She knows people have to see her as president, Brinkley said.

Of course, should Trump win the election next month and serve a full second term, Pence could himself run to be the 46th president in 2024 or run to be the 47th president should Trump lose.

His prospects in the latter scenario, however, would depend on the margin of Trumps loss, whether Republicans also lose control of the Senate, and the complexion of a post-Trump party, particularly if Trump loses badly.

Its really hard to tell at this moment what will be left of the GOP at all if Trump gets creamed, said Amanda Carpenter, a former aide to Sen. Ted Cruz (R-Texas), who is likely to run for the presidency again after losing to Trump in the 2016 primaries. It could end up as a really small party of bitter-enders.

We want to know what youre hearing on the ground from the candidates. If you get any interesting or suspicious! campaign mailers, robocalls or hear anything else you think we should know about, email us at scoops@huffpost.com.

CORRECTION: An earlier version of this story misstated Joe Bidens age. He is 77 now (and will turn 78 in late November).