MINNEAPOLIS (WCCO) — The race for Minnesota’s 8th Congressional District is turning out to be one of the most expensive in the country.

Not only are the candidates spending millions of their own campaign dollars, but millions more from outside groups is pouring in.

READ MORE: Violence Free Minnesota Finds Help For Domestic Abuse Survivors

So far, $10.5 million from outside groups has helped fuel the TV onslaught.

On top of that, Rep. Rick Nolan and challenger Stewart Mills have spent more than $5 million on their own.

One reason there’s so much money involved is because, according to both sides, the race is close.

While there are only about 25 or so congressional races that have the potential to flip from one party to the other, this is one of the few districts that has recently gone back and forth.

In the last six years, the district has flipped from Democrat to Republican and back to Democrat.

In 2014, Nolan beat Mills by less than 4,000 votes.

READ MORE: Saint Paul Regional Water Services Is Well-Equipped To Handle Heat And Drought

“There is probably only about four or five seats where we have seen it flip back and forth like the 8th District,” Hamline University political science professor David Schultz said. “So this might be one of the most competitive races in the country.”

With both parties fighting for control of Congress, a win in the 8th District is key for both sides.

Another factor is that the sprawling district includes the TV markets of both Duluth and the Twin Cities, meaning the campaigns and outside groups need to buy ads in both markets.

And then there is the Trump factor.

Republican presidential nominee Donald Trump leads rival Hillary Clinton among white, non-college-educated men by a stunning 76 percent to 17 percent in the 8th District.

Trump’s lead is so great in this demographic that it could have a coattail effect that might help Mills.

With only two weeks left until the election and more money continuing to pour in, overall spending in this race could possibly exceed $20 million.

MORE NEWS: What Health Information Can Employers Require From Their Workers?

Meanwhile, Vice President Joe Biden will be in Duluth Friday to campaign for Nolan and Clinton, sources tell WCCO.

Esme Murphy