Bernie Sanders is using a back-waxing video to promote his campaign

Over the last few days, a few different people on Twitter (a Re/code reporter included) spotted what looked at first glance like a BuzzFeed Twitter video promoted by the Bernie Sanders presidential campaign.

https://twitter.com/nkulw/status/721844243308941313

For someone casually scrolling down her Twitter feed, it might seem as though the Vermont socialist was paying to sponsor BuzzFeed videos. If you actually clicked on the video (which has since been deleted), a pre-roll Sanders ad showed up, which alleviated some of the confusion.

But that fundamental weirdness still remains, highlighting what has been a particularly thorny issue for all candidates running in the 2016 election. Programmatic ad buying — that is, using software to automate the buying process — can place political ads next to content on YouTube, Twitter and elsewhere that the candidates obviously don’t endorse.

Increasingly, campaigns rely on digital platforms and programmatic ad buying to influence voters. Analysts — Nomura’s Anthony DiClemente included — estimate political spending in the 2016 election cycle will reach $1 billion, roughly five times the amount invested in 2012.

The biggest beneficiaries of the surge in digital ad spending are Facebook and Google parent Alphabet, which boast the biggest online audiences and sophisticated tools for reaching potential voters.

When reached for comment on the Twitter-BuzzFeed promotions, the Sanders campaign made it clear that it didn’t choose which specific BuzzFeed videos — like, say, waxing — in which it was running ads. Digital director Kenneth Pennington said the campaign was advertising against all BuzzFeed videos.

The campaign, in turn, promoted the BuzzFeed video on Twitter, using targeting software known as Amplify that allows advertisers to reach an audience based on location, age, gender or interests. It’s this Amplify service that makes it look like the Sanders campaign was promoting the BuzzFeed video instead of the ad that it placed for users who actually opened up and watched the video.

The Sanders promotion also meant that the BuzzFeed videos appeared in front of audiences that would not normally see them: Likely voters in yesterday’s New York primary. Pennington did not immediately respond to questions about whom the campaign hoped to reach.

When reached for comment, BuzzFeed spokesperson Liz Wasden said, “We test with all kinds of products across many platforms, including this one with Twitter’s Amplify product.”

This article originally appeared on Recode.net.