President Trump's job approval has slumped in three key states that helped him win the election last year.

According to a trio of new NBC News/Marist polls released Sunday morning, Trump's approval is below 40 percent among registered voters in Michigan (36 percent), Pennsylvania (35 percent) and Wisconsin (34 percent).

The three states provided Trump 46 electoral votes in the 2016 presidential election, becoming the first Republican nominee to carry them since the 1980s.

In all three states, Trump's disapproval ratings are above 50 percent. Another two-thirds of those voters polled said they are embarrassed by Trump's presidential conduct.

The poll also revealed that voters in the three states said they would prefer Democrats to control Congress after the 2018 midterm elections. In Michigan and Wisconsin, Democrats have a double-digit advantage on that question, and have an eight-point lead in Wisconsin.

The polls were conducted after the violence in Charlottesville, Va., last weekend and amid Trump's multiple comments on the clashes between white supremacists and anti-racism counter-protesters.

Pollsters surveyed roughly 800 registered voters in all three states between Aug. 13-17. The margin of error for all three is plus or minus 3.5 percentage points.