A super PAC aligned with Senate Majority Leader Mitch McConnell gave another $8.5 million to Defend Arizona, a PAC that supports U.S. Senate candidate Martha McSally and has run ads painting Democrat U.S. Senate candidate Kyrsten Sinema as a radical liberal, according to a report with the Federal Election Commission.

Senate Leadership Fund, and other McConnell allies, have already invested more by far in Arizona's U.S. Senate race than any other group.

So far in October, SLF has made four donations to Defend Arizona.

On Oct. 3, SLF sent $2 million to the PAC. And the day after, another $2 million.

A week later on Oct. 11, SLF sent another $3.5 million to Defend Arizona.

Five days later, the PAC received $1 million more from SLF.

Barrett Marson, a spokesman for Defend Arizona, said that the money is being spent on voter contact to show why McSally would better represent Arizona.

"(Senate Minority Leader) Chuck Schumer has invested heavily in this race to get another seat, another reliable liberal vote out of Kyrsten Sinema," Marson said.

McSally, a two-term congresswoman from the Tucson-based 2nd Congressional District, is locked in a tight battle against Democratic challenger Sinema, a three-term congresswoman from the Phoenix-area 9th Congressional District.

This fight for retiring Republican Sen. Jeff Flake's seat is coveted by both parties so there's been a significant amount of money poured in from both sides.

Marson rejected the notion that McSally is someone McConnell, R-Kentucky, believes he can control.

"Martha McSally has been a strong independent voice throughout her career," he said, adding that her record shows it.

James Owens, a spokesman from the Sinema campaign, said that McSally "does what her party bosses tell her to do 98 percent of the time, even when it means cutting protections for Arizonans with pre-existing conditions."

"Mitch McConnell has already announced plans to cut Social Security and Medicare, and he knows that Congresswoman McSally will be a reliable vote for that agenda no matter the price Arizona families pay," he added.

READ MORE: