How do you compete with Beto O’Rourke, the dynamic, guitar-playing, skateboarding Democrat who’s threatening to take your Senate seat? If you’re Ted Cruz, you compare yourself to a serial killer.

On Halloween, the Texas Republican senator’s official Twitter account tweeted an image of one of the Zodiac Killer’s mysterious letters, with the caption “Happy Halloween,” referencing the meme that Cruz himself is the serial killer who terrorized California in the 1970s.

The conspiracy theory apparently first popped up in 2013, when a Twitter account made a joke that Ted Cruz was giving a speech titled “This Is the Zodiac Speaking,” referencing a letter the never-caught killer sent to the San Francisco Chronicle. The Zodiac Killer committed their first murder in 1968, so it’s unlikely that Cruz, who was born in 1970, is the actual killer. But the meme captured public imagination during the 2016 Republican primary when Cruz was facing off with President Donald Trump.

It might seem like a strange last-minute publicity move, to an impartial observer, for Cruz to compare himself to a killer who claimed 37 murders. But then, Cruz isn’t known as the most likable person to begin with. His own college roommate spoke out during the primary to claim that everyone hates him.