One's a Republcian contender for the US presidency; the other is an unidentified serial killer who stalked north California in the 1960s and 70s and may have murdered up to 28 people.

But for a surprising number of Americans, they could be one and the same person.

More than a third of people surveyed in a Florida poll thinks Republican presidential candidate Ted Cruz could be the mysterious Zodiac killer.

In a poll that revealed Donald Trump was easily leading nearest rival Marco Rubio head-to-head in the Sunshine State, some people seemed more concerned with the results of the survey’s final question: “Do you think Ted Cruz is the Zodiac killer, or not?”

Of Floridians polled, 10 per cent said yes, 62 per cent said no and 28 per cent were unsure - meaning 38 per cent were not entirely ruling out the theory.

Ahead of the GOP presidential debate on Thursday night, US polling firm Public Policy Polling asked its Twitter followers to decide its final poll question – with the overwhelming winner being the Cruz/Zodiac conundrum.

Ted Cruz speaks at a rally in Houston, accompanied by Texas governor Greg Abbott (AP)

The Zodiac killings are one of the most enduring murder mysteries in recent American history.

Between 1968 and 1969 a serial killer murdered two men and three women, either by shooting or stabbing them.

The killer taunted police and press with a series of cryptic messages, in which he identified himself using the Zodiac sign. He was never found and could have killed dozens more.

A film about the killings, Zodiac, starring Jake Gyllenhall, was released in 2007.

The link between Ted Cruz and the Zodiac killer, though frivolous, is well established.

A tweet jokingly claiming Cruz and the Zodiac were one and the same first appeared in 2013, according to the Daily Dot.

As the GOP’s presidential candidate race has heated up, the gag has snowballed, to the point that a Google search of Cruz’s name brings up the Zodiac killer as one of the top results.