Washington DC - A new poll released Wednesday shows Kamala Harris with significant leads over Donald Trump in swing states Pennsylvania and Michigan, two "blue wall" battlegrounds seen as key to winning the White House in November.

The surveys, conducted after the September 10 televised debate between the two candidates, suggest a post-showdown boost for Vice President Harris, who is widely perceived as having outperformed her Republican opponent on stage.

In the latest poll of likely voters by Quinnipiac University, Harris is leading ex-president Trump 51% to 45% in Pennsylvania and tops him 50-45% in Michigan, two states in the post-industrial Rust Belt in the American Midwest and Northeast.

A third Rust Belt state that makes up a trio seen as vital for a Harris victory, Wisconsin, has the race essentially tied, with Harris one percentage point ahead, according to Quinnipiac.

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Overall polling shows the tightest of races in the seven battleground states that will likely determine the winner in the US Electoral College system.

Trump leads narrowly in the so-called Sun Belt states of Arizona, Georgia, and North Carolina, according to an amalgam of polls on survey tracker RealClearPolitics.com. It shows Harris barely ahead in the fourth Sun Belt state of Nevada.

The Pennsylvania poll of 1,331 likely voters is notable as Harris's six-point margin is outside Quinnipiac's 2.7% margin of error – and twice the same poll's margin of three percentage points in August.

"Three crucial swing states wave a red flag at the Trump campaign," Quinnipiac University Polling analyst Tim Malloy said in a statement, noting that the Republican Party's typical "attack strategies against Democrats on immigration and the economy may be losing momentum."

Harris only became the Democratic Party's presidential candidate in July, after President Joe Biden dramatically ended his own reelection bid following a disastrous debate performance against Trump.

Her entrance provided an energetic jolt to the party and she has fared better against Trump than Biden did in the polls. Recent weeks have been seen as critical for Harris as voters have limited time to get to know the vice president and her policies before Election Day on November 5.

The latest ABC News/Ipsos national poll, post-debate, shows Harris with a four-point overall lead, while a post-debate Atlas Intel poll has Trump ahead by three percentage points nationally.