The US election is only five days away and both the Hillary Clinton and Donald Trump campaigns are focusing on what political professionals call "Get Out The Vote". That is to say, rather than try to persuade new people to vote for them, all efforts are now focused on getting existing supporters to the polling booth.
That's why all sorts of celebrities have started putting out videos urging people to vote. They especially want to attract notoriously unreliable younger voters, who if they do turn out could swing the election decisively for Hillary.
Earlier today, the Clinton campaign dropped the below video, featuring Will Ferrell.
Will Ferrell: comedian, actor, just your average millennial. pic.twitter.com/ExfbQX3AS1
— Hillary Clinton (@HillaryClinton) November 4, 2016
Okay, that's pretty funny, right? Look, it's an old man pretending to be down with the kids by talking about apps. Brilliant.
But what you might not have spotted is a hidden psychological trick.
"Our voting record is public record", Ferrell reminds viewers, "that's right bae, whether we vote or not is available online".
"If you don't vote, everyone might find out that you're the opposite of on fleek", he warns.
Amazingly this is actually some pretty sound political science at work.
Ferrell's claim, that voting records are public, is actually true. In the US, records of whether you voted or not are public. (Who you actually voted for, of course, remains secret.)
This enabled Professor Donald Green from Yale to carry out an experiment on the impact of social pressure on elections. Here's how the American Psychological Association described the experiment's setup:
"He conducted an experiment involving 180,000 Michigan households for the 2006 primary elections. About half of the group was the control group, and did not receive any mailed communication. The other half was divided into four groups, each targeted with a different mailing.
People in the first group got a letter reminding them of the importance of doing their civic duty and voting. The second group received the same message, but they were also told that voting records were public records, and that their turnout was being studied. The third group got a letter listing whether or not they had voted in the last two elections, and were told that after the election, another letter would be sent to them indicating whether they voted in the upcoming election.
The fourth group received a letter listing whether their neighbors had voted in the previous two elections, and told them that after the election, another letter would be sent out to them and their neighbors with a check mark next to their names indicating whether or not they had voted."
The results were rather striking. Among the fourth group turnout increased by 8.1%. The slightly less intimidating measures were effective too: Turnout shot up by 4.9% among the group who were shown their own voting records, and 2.5% among people who were in the second group with the letter saying they were being studied. Even turnout among the first group, who were simply told that voting is important in a letter increased turnout by 1.8%.
Given how close elections can be, these numbers are huge. If turnout can be driven up by even just 2.5%, that could easily be enough to tip an election.
In other words, by receiving this nudge, it got people out to the polls. And turning the screws by talking about sharing the receivers' voting record with their neighbours, it really put the social pressure on and increased turnout hugely.
So how does apply to Will Ferrell? "If you don't vote, everyone might find out that you're the opposite of on fleek", might sound like a joke - but it's actually using this exact same psychological trick to try to scare voters into getting down to the polls.
We shouldn't be surprised that the Clinton campaign is using research in this way - all major political campaigns do it. But it's fascinating to see what has been learned by academics being applied in practice.