Senate Minority Leader Harry Reid (D-NV) listens to questions from reporters during a news conference after their weekly policy meeting with Senate Republicans, at the U.S. Capitol, May 10, 2016. Drew Angerer/Getty Images

With control of the Senate hanging in the balance, one of the most hard-fought congressional races this year will be Nevada’s contest to replace retiring Democratic leader Harry Reid. The race has already been inundated with millions of dollars in outside spending, including a $1.2 million ad buy announced this week by a super PAC connected to the libertarian billionaire brothers Charles and David Koch.

The super PAC, Freedom Partners Action Fund, said it will run television and web ads attacking Democratic candidate Catherine Cortez Masto’s record as Nevada attorney general. The ad being circulated accuses her of targeting the transportation company Uber and forcing it out of the state in order to protect the taxi industry.

“Many Nevadans turned to Uber for work,” says the voiceover narration in the Freedom Partners ad. “But, after accepting more than $70,000 from taxi companies, Catherine Cortez Masto went after Uber — once, twice, three times — until she drove them out of town, along with all their jobs. She put campaign donors ahead of Nevadans and protected special interests instead of us.”

Reporter Jon Ralston of the Reno Gazette-Journal described the ad as “BS,” something that the Cortez Masto campaign noted in its Monday statement replying to Freedom Partners.

“The truth is: ride-sharing companies were operating in Nevada without a license and the Transportation Authority requested that the Attorney General’s office enforce the law to protect passenger safety,” said the Cortez Masto campaign. “Ride-sharing companies then sought licensing through the legislative process and are now operating legally in Nevada.”

Freedom Partners is far from the only national conservative group getting involved in the race. Three other right-leaning super PACs — John Bolton Super PAC, Americas PAC and the closed-borders group Secure America Now — have each spent tens of thousands of dollars in the race thus far, according to the Center for Responsive Politics. Additionally, the United States Chamber of Commerce has thrown more than $2 million behind Republican candidate Joe Heck, currently a member of the House.

On the Democratic side, a super PAC affiliated with Planned Parenthood has spent approximately $75,000 in the race, and the Senate Majority PAC has put in nearly $1 million.

Sunlight Foundation policy analyst Richard Skinner told International Business Times that those high spending levels are “pretty much standard these days for a hotly contested Senate race.”

“It’s normal in the post-Citizens United world,” said Skinner, referring to the 2010 Supreme Court decision that kicked off the era of unlimited super PAC spending. “I would say that even prior to Citizens United, the long-term trend for congressional elections was for them to become more nationalized, more partisan.”

The Nevada race is likely to be especially tough — and expensive — because it’s over one of just a handful of Senate races that could decide which party commands a majority during the next president’s first two years of office.

“This could be the seat that makes the difference,” said Skinner.