After news broke Sunday of Democratic presidential nominee Hillary Clinton's pneumonia, some pundits and journalists began speculating that she might drop out of the upcoming election. 

Her replacement? Possibly Vice President Joe Biden.

The rumors started flying Monday morning when NPR political analyst Cokie Roberts claimed Clinton's emergency departure from a 9/11 event over the weekend had Democratic leaders "very nervously beginning to whisper about having her step aside and finding another candidate." She debunked the idea, but added that "ironically, the candidate that everybody looks at is Joe Biden," the Washington Post reported. Then former Al Jazeera America reporter David Shuster tweeted that a Democratic National Committee delegate told him there was "every indication" they'd back Biden instead of Clinton's one-time rival Bernie Sanders or her running mate Tim Kaine.

In theory, it is possible one of them could replace Clinton. The charter and bylaws of the Democratic party lays out the process for what happens when a vacancy on the presidential ticket occurs. 

"Special meetings of the National Committee may be held upon the call of the Chairperson with the approval of the Executive Committee with reasonable notice to the members, and no action may be taken at such a special meeting unless such proposed action was included in the notice of the special meeting," the document reads. "The foregoing notwithstanding, a special meeting to fill a vacancy on the National ticket shall be held on the call of the Chairperson."

Proxy voting would not be allowed, CNBC reported. But that's not the only hurdle.

Because the election is so close, many states have already approved the names of candidates due to appear on their ballots, according to Paste. So the issue of replacing Clinton would then go to the courts.

It's unclear whether Biden would even be interested in the nomination. The vice president revealed last October that he did not plan to run for president, saying his window to launch a solid campaign had closed and referencing his ongoing recovery from the death of his son. In January, though, he told NBC Connecticut he regretted not running "every day, but it was the right decision for my family and for me."

Biden has campaigned on Clinton's behalf.