Hillary Clinton speaks to reporters after holding a "National Security Working Session" with national security advisors in New York, U.S. September 9, 2016. REUTERS/Brian Snyder Hillary Clinton's recent health episode stirred speculation on what would happen if she dropped out of the race before Election Day.

A former Democratic National Committee chairman told Politico on Monday that the party should start coming up with a contingency plan should Clinton need to exit the race.

"Now is the time for all good political leaders to come to the aid of their party," said Don Fowler, who led the committee from 1995 to 1997. "I think the plan should be developed by 6 o’clock this afternoon."

Fowler said "you would be a fool not to prepare" a back-up plan.

So what would happen if Clinton dropped out? The rules on replacing candidates vary from party to party.

The Democratic Party's rules, which are similar to the Republican party's, state that the party chairperson would have to call a special meeting to fill any vacancy on the national ticket, according to AFP. The decision on who should fill the vacancy would be based on a majority vote from those who attend the meeting.

The Republican rules are similar, AFP noted.

If the rules for replacing presidential candidates seem vague, it's by design.

"It gives them the opportunity to make the best decision, rather than tie their hands with some kind of process that would give them a nominee they will not be comfortable with," Jeanne Zaino, a professor of political science at Iona College in New York, told AFP.

Clinton is taking a break from campaigning while she recovers from pneumonia. She was diagnosed with the illness on Friday, and her campaign announced it to the public on Sunday when she had to leave a 9/11 memorial event early because she was feeling "overheated."

Campaign spokesman Brian Fallon said she expects to be back on the trail later this week, and Clinton herself tweeted Monday afternoon that she's "anxious to get back out there."

But questions about her health have surfaced recently as she's been seen with a bad cough at speaking events.

Fallon, however, said "there is no other undisclosed condition" Clinton suffers from.