Joe Biden accused South Bend, Indiana, Mayor Pete Buttigieg of copying his healthcare proposal.

Biden leveled the accusation while speaking to reporters on his campaign bus in Iowa on Monday evening, according to Reuters. Biden has pushed for a revamped version of the Affordable Care Act, also known as Obamacare, the landmark healthcare legislation backed by former President Barack Obama.

Biden has said he would add a "public option" to the plan that would allow people to opt into the government healthcare system, but only if they wanted to. Otherwise, Americans would keep their private insurance plans.

Buttigieg's healthcare proposal would allow for private and government insurance plans. He has billed the proposal as "Medicare for all who want it."

"He stole it," Biden said while accusing the media of holding a double standard. "What would you have done to me? You’d have torn my ears off."

Buttigieg's campaign pushed back against Biden’s claim, noting that the South Bend mayor has been using the "Medicare for all who want it" line since before Biden launched his presidential campaign in April.

Buttigieg has a commanding lead in the latest Iowa poll on the Democratic presidential primary contest. Buttigieg sits first at 25% and with a 9-point lead over Massachusetts Sen. Elizabeth Warren, who polled at 16%. Biden is tied for third with Vermont Sen. Bernie Sanders at 15%, according to a CNN/Des Moines Register survey released in mid-November.