No other circus has ever drawn more.

Nielsen, a television ratings company, estimated Friday that 51.4 million viewers watched at home on one of the 12 rated networks that showed the debate. Nielsen’s total did not include television viewers in offices, restaurants, bars, or other areas, nor did it include any Web viewers.

The Oct. 3 debate between President Obama and Mitt Romney garnered about 67.2 million viewers at home, according to Nielsen, and untold millions more via the Web.

Unlike Mr. Obama and Mr. Romney, Mr. Biden and Mr. Ryan had stiff competition from two big sporting events: a baseball playoff game between the Yankees and the Orioles and an NFL match-up between the Steelers and the Titans. Both games were watched by between 5 and 6 million viewers, potentially deflating the vice presidential debate audience.

Here’s a ratings chart of prior VP debates for comparison. The Palin/Biden match four years ago is in a class by itself, but until last night, the only other to crack 50 million was Bush/Ferraro in 1984. No surprise that debates featuring the first Republican and Democratic women on the tickets would be big draws. More than half of last night’s viewers were over 55, which, per Politico, may explain why Biden addressed the camera directly when talking about seniors. It might also explain his theatrical disdain for Ryan: Seniors lean Republican and they’ve proved more or less immune to Democratic Mediscaring so far, so maybe Greasy Joe figured the way to make them waver was to show that the young guy simply isn’t worth taking seriously.

Here’s fair-and-balanced newsman David Shuster dutifully rattling off the party line on Current TV, capped by the surreal assertion that Biden just made himself the frontrunner in 2016. Back in reality, if the Democratic field proved so incredibly weak in four years that The Joker really did emerge as likely nominee, Hillary would be drafted by panicky party elders and would roundly crush him in the primaries. No one believes her when she says she’s tired of politics, but even if she is, the fact that the only thing standing between her and becoming the first major party woman nominee is a guy prone to remarking aloud about how many Indians work at 7-11 would ultimately draw her in. Easy pickings.

But since we’re talking about unlikely electoral realities, here’s your sinister exit question via a trouble-making Philip Klein: Could Biden end up becoming … Romney’s VP? Click the image to watch.