A last-minute video produced by the city Board of Elections shows voters how to cast a ballot in Tuesday’s election — with a clear bias toward Gov. Cuomo.

The 55-second online video features images of the two-page ballot, with a darkened oval over Cuomo’s name in the first position near the upper-left-hand corner of the first page.

Republican challenger Marc Molinaro on Sunday accused city election officials of trying to sabotage his underdog campaign against the two-term incumbent.

“New York State is rigged to preserve the ‘status Cuomo’, and here we see another not-so-cute example of it,” Molinaro said.

“This governor and his cohorts will stop at nothing to give him every possible advantage, regardless of what it costs taxpayers.”

In addition to showing a vote for Cuomo, the ballot in the instructional video — posted online Saturday — also carries marks for multiple candidates in several races, meaning it would be thrown out for illegal “overvoting” if actually submitted.

In the line for governor, the ballot shows an additional vote for Libertarian Party candidate Larry Sharpe, while the line for comptroller shows a minor-party vote for incumbent Democrat Thomas DiNapoli and another for Republican challenger Jonathan Trichter.

A whistleblower noticed the politically problematic snafus and alerted Molinaro via his “Cuomo Leaks” Web site for anti-corruption tipsters, Molinaro’s campaign said.

“The video clearly shows the ballot marked with a vote for Andrew Cuomo. It then shows a pencil bubbling in a vote for a Democratic judge,” the whistleblower wrote in a message to Molinaro.

“It then shows a pencil bubbling in a vote for a Democratic judge. This hardly seems impartial from the agency charged with administering the elections impartially.”

The tipster also called the overvoting on the ballot “even dumber,” saying that “a video instructing voters how to vote actually shows them improperly.”

The video, titled “Mark It, Tear It, Scan It,” was posted on YouTube and the Board of Elections Web site.

There are versions with narration in English, Spanish, Russian, Korean, Chinese and Bengali.

As of Sunday evening, the English version had racked up 795 views and six “likes.”

A spokeswoman for the city Board of Elections declined to comment.

Cuomo campaign spokeswoman Abbey Collins said: “We know the Molinaro campaign is desperate, but any credible candidate for governor should know that the City Board of Elections is an independent board with absolutely no connection to the governor or his campaign.”