ObamaCare co-architect Jonathan Gruber -- who infamously said “the stupidity of the American voter” helped get the measure to become law -- now blames Trump for rising premium costs.

“Whose fault is this?” Gruber asked on “Fox News Sunday.” “Since President Trump has been elected … premiums are going up and insurers are exiting.”

Gruber, a Massachusetts Institute of Technology economics professor, argued that perceived rising premium costs are really a one-time increase in 2016 to cover “massively underpriced” policies for the first two years of the 2010 law.

He also said the increase “fixed” the problem because insurance companies then showed signs of profitability and talked optimistically about continued participation in the program.

Right now, major ObamaCare insurers are pulling out of Iowa and Virginia exchanges, leaving many customers with one or no options and putting the state exchanges in jeopardy of collapse.

Gruber also argued Sunday that Trump contributed to ObamaCare’s rising prices and fewer policy options for Americans because he “undercuts open enrollment.”

Trump shortly after taking office cut advertising days before the January 2017 signup deadline.

Gruber was never part of the Obama administration but was a top adviser, purportedly paid hundreds of thousands of dollars for his input.

He is seen and heard on several videos after the law was passed talking about the political tactics used to garner public support.

In a video that surfaced in 2014, Gruber is heard saying the administration called the so-called “Cadillac tax” on top-shelf, employer-based plans a tax on insurance policies, not people, to exploit voters’ “lack of economic understanding.”

In another video, Gruber says, “The stupidity of the American voter … was really critical for the thing to pass.”