A new batch of polls cast doubt on Donald Trump's theoretical path to victory over Hillary Clinton

Donald Trump has maintained throughout the campaign that his path to winning the White House cuts through the working-class Rust Belt states that President Barack Obama won in 2008.

But new evidence shows he might have a problem following that path.

A new series of Bloomberg polls released Thursday found that middle-income voters in Michigan, Wisconsin, and Ohio backed Democratic presidential frontrunner Hillary Clinton over Trump by 7 points.

According to Bloomberg, the voting group - comprised of individuals making between $30,000 and $75,000 a year - is a key voting bloc that represents nearly 40% of eligible voters who cast ballots in the three states in recent elections.

Most polls conducted over the last several months have shown Clinton with a healthy lead in states like Michigan and Wisconsin, though Trump has climbed in national polls in recent weeks.

Some evidence suggests that Trump may have already scrambled the map, but not in a way that his campaign would prefer. Polls in Arizona and Georgia have displayed a tighter race between Trump and Clinton that many experts attribute to Trump's inflammatory rhetoric.

Despite the public polling, Trump's frequent assertion that he could woo working class white voters has startled some Democrats. Clinton's campaign is doubling down its efforts to hold states like Michigan and Ohio, which Obama won in 2008 and 2012.

But some experts caution not to overestimate Trump's ability to alter the electoral landscape just yet.

Princeton polling expert Sam Wang told Business Insider earlier this week that so far, the map looks similar to recent presidential contests.

"So far things are looking more simple than he is making out," Wang said.

Wang added: "Polls so far show almost every state in the same 'rank order' ... R's stronger in GA than NC, stronger in NC than PA, the same order as in 2000-2012. All will be lifted together by the same tide, or fall together."