Trump's approval rating remains markedly underwater in key battleground states, where he's making the upcoming midterm elections even bleaker for Republican candidates.

Not only is Donald Trump historically unpopular for a first-year president, but he’s especially unpopular in states that will serve as critical battlegrounds during the November midterm elections.

That’s confirmed by a new batch of state-by-state polls from Gallup that highlights the potential losses looming for the GOP.

Democrats need to flip 24 seats to gain control of the House. According to the Cook Political Report, of the 62 Republican-held districts currently deemed to be “competitive” in November 2018, 25 of those are located in California, New Jersey, New York, Ohio, and Pennsylvania.

In all of those states, Trump’s approval rating remains underwater. And in a few of them, he is out-and-out detested.

In California, where Republicans are clinging to their 14 congressional seats, Trump’s approval rating is a paltry 29 percent. In New York, it’s only one point higher. And in New Jersey, it reaches a mere 34 percent.

Trump fares slightly better in Pennsylvania, with 42 percent, and Ohio, with 45 percent. But in none of the states does he clear the 50 percent mark. And that’s a big deal.

Because historically, when new presidents hit the midterms with a 50 percent approval rating or higher, their party only loses an average of 14 seats in the House. If presidents are below 50 percent, their party loses 34 seats.

Today, Trump’s approval rating stands at 38 percent. He peaked at 45 percent 12 months ago. In terms of individual states, it remains above water in only 12 states, according to Gallup.

Trump retains his highest level of support in sparsely populated states, such as West Virginia, Montana, and North and South Dakota. By contrast, he’s widely disliked in the country’s most populous states, such as the aforementioned California and New York, as well as the sixth most populous state of Illinois.

Even in the traditionally Republican state of Texas, Trump’s approval rating has fallen all the way down to 39 percent.

Trump is an anchor around the necks of Republicans — likely why more and more of them are calling it quits.

On Monday, New Jersey Rep. Rodney Frelinghuysen announced his retirement, and he’s a telling case. A veteran politician who comes from a famous, wealthy New Jersey family, Frelinghuysen spent his 20-year career in the House cruising to re-election victories for the last 20 years. He won in 2016 by 20 points.

But with the tide turning so strongly against Trump, especially in increasingly blue bastions like New Jersey, the powerful chairman of the House Appropriations Committee opted to bow out, rather than face angry local voters in November.

Today, it’s a greatly daunting task to run for re-election as a Republican in a number of key states, thanks to Trump and his toxic agenda. The odds of a widespread Republican wipeout are increasing every day Trump remains as a stain on the office of the presidency.