President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's approval rating among his supporters in the Midwest appears to be declining, according to a series of Hill-HarrisX polls since July.

Of those surveyed, 47 percent of Midwest voters said they approved of Trump's job in office last July, with his highest mark among those voters reaching 54 percent in the months of October and December.

In the latest Hill-HarrisX survey in February that number had slipped to only 40 percent of Midwestern voters saying they approved of the president.

The polls also show rising disapproval of Trump among Midwest states, with 53 percent saying they disapproved of Trump in July and 60 percent saying the same in February.

The trend could end up being a problem for Trump, who scored crucial victories in 2016 in Midwest states like Wisconsin and Michigan, helping to propel him to an electoral college victory.

"When it gets down to it, the president is going to get reelected or defeated on a state-by-state basis," Chris Wilson, chief strategist at WPA Intelligence, told Hill.TV'S Krystal Ball on Wednesday.

"So the numbers I'm most concerned about are those in states like Michigan, and Pennsylvania, and Iowa, and Wisconsin. States that he won last time that Republicans hadn't won in a longtime," he continued.

Trump's approval ratings also saw a decline in the south, another political stronghold for him.

Fifty-two percent of southern voters said they approved of him in July and now 46 percent say they approve of him in that region.

There was also a rise in the president's disapproval rating in the south, with 48 percent saying they disapproved of him in July, and 54 percent saying the same in February.

Trump's national approval rating currently sits at 45 percent, according to the latest poll, while his disapproval rating is at 55 percent.

The states included in the Midwest category were Illinois, Indiana, Michigan, Ohio, Wisconsin, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, and South Dakota.

The Southern states were Delaware, Washington, D.C., Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia, West Virginia, Alabama, Kentucky, Mississippi, Tennessee, Arkansas, Louisiana, Oklahoma, and Texas.

The polls were conducted among statistically representative samples of about 1,000 registered voters. Each of them has a sampling margin of error of plus or minus 3.1 percentage points.

— Julia Manchester