A few things…

First, this is an opinion piece.

Second, it is highly unlikely that there is any quantitative evidence regarding the impact of two obscure videos. I’m sure the campaigns have conducted focus groups regarding these videos, but I highly doubt that there will be a 1,000+ sample size attitudinal data analysis of the impact of these videos on the electorate.

Third, polling in the primaries, especially exit polling, shows that Biden has problems with younger voters. However, it isn’t just vote choice, but whether younger voters will abstain. Therefore, younger voters could be turned off, but the results won’t show in any exit polls on Election Day (for example) because they decided not to participate in the election. Turnout is more important than vote choice with 30-and-younger voters (ask Bernie).

Fourth, asking about quantitative evidence misses the point. This isn’t about results, but about campaign tactics. The qualitative evidence on its face shows that these videos don’t seem to be relatable to younger voters (hence the reason you aren’t seeing young voters flocking to Biden quite yet). The ad by Biden seems out of touch. The Trump ad does have a target audience with an electoral call-to-action.

Fifth, which is somewhat related to the fourth, is that I find that academics (as a practice, not as individuals) cannot explain electoral strategies. Though I am a political scientist myself, I also worked in the practical field for 28 years. I feel that a lot of political scientists lack any type of practical understanding in the field of politics itself, and just use politics to show off their latest Monte Carlo simulations or something like that. Basically, their theories are not based on a practical understanding of the political world. Therefore, quantitative research methods aren’t always going to produce the best results (which is also why I believe (opinion) that half of the papers presented at Palmer House are practically useless).