To get people watching live video online, add suspense.

After just two rounds, internet viewing of the NCAA men’s basketball tournament has already surpassed last year’s total, with 51 million video streams, according to the broadcasters involved. That’s despite many of the games requiring a pay TV subscription to watch online.

New data suggest much of the streaming has concentrated on the final minutes of nail-biting upsets. The underdog has been victorious in all five of the most popular games so far:

No. 11 Dayton (60) beats no. 6 Ohio State (59) — 4.6 million streams

No. 14 Mercer (78) beats no. 3 Duke (71) — 4.2 million

No. 12 Harvard (61) beats no. 5 Cincinnati (57) — 2.8 million

No. 8 Kentucky (78) beats no. 1 Wichita State (76) — 2.0 million

No. 10 Stanford (58) beats no. 7 New Mexico (53) — 1.5 million

Ratings for traditional TV are generally reported as an average number of viewers over the entire program. Not so with internet TV. Dayton’s upset of Ohio State, for instance, totaled 4.6 million streams during the course of the game, with most people presumably tuning in just for the conclusion. That is supported by overall internet viewing time, which is up just 6% from the same point in last year’s tournament, even though the number of streams is up 40%.

The figures imply more people this year are watching online for shorter time periods—perhaps drawn in at the climax by chatter on social media.

Intense interest in the most suspenseful moments of March Madness could point to a strategy for companies trying to get people to watch video online. Drama-filled bursts of live action—like Felix Baumgartner’s space jump sponsored by Red Bull, which was viewed by 8 million people at the same time—seem to possess a congregating power on a par with cable television. But getting people to stay connected for the entire program is more difficult, perhaps impossible.

It has certainly helped that live streams of the NCAA tournament have appeared to work flawlessly for most users, unlike ABC’s mangled stream of the Oscars and other recent internet video snafus. The games are available on the web and through apps for Apple and Android phones and tablets. Mobile streams of the tournament are up 74% from last year.

Last month’s Winter Olympics was also heavily watched online, despite similarly requiring a pay TV subscription to watch. NBCUniversal reported that 2.1 million people online live-streamed a tense semi-final match between the US and Canada’s men’s hockey teams.