National Republicans are pouring in money to sink ex-coal CEO Don Blankenship's GOP campaign for the Senate one week ahead of the Republican primary in West Virginia.

Mountain Families PAC, based out of Arlington, Va., is spending an additional $585,000 against Blankenship, according to filings made to the Federal Election Commission (FEC) over the weekend.

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The investment comes on top of the roughly $743,000 the group pumped into the race earlier this month, bringing their total spending against Blankenship to more than $1.3 million in roughly two weeks.

A bulk of the spending is going toward running TV ads against Blankenship, according to FEC records.

An ad, uploaded to YouTube late last week , knocks Blankenship over the Upper Big Branch mining disaster, where 29 miners were killed in an explosion. Blankenship was sentenced to prison for a year for conspiring to violate mine safety standards.

"Don Blankenship was about the money; West Virginia families paid the price," the ad's narrator says.

An earlier ad from the group compared Blankenship to "toxic sludge."

The group is also spending money on online advertising.

National Republicans haven't publicly aligned themselves with the outside group, but the PAC has deep ties to the party and its allies in Washington.

The influx of new money against Blankenship comes as the anti-establishment candidate appears to be fading into third place in recent polling.

A recent Fox News poll showed Blankenship with 16 percent support among Republican voters, behind Attorney General Patrick Morrisey and Rep. Evan Jenkins Evan Hollin JenkinsWest Virginia New Members 2019 Republican Carol Miller holds off Democrat in West Virginia House race Trump to fundraise for 3 Republicans running for open seats: report MORE — who were at 21 and 25 percent, respectively.

The candidates are running for the GOP nomination to take on Sen. Joe Manchin Joseph (Joe) ManchinThe Hill's Morning Report - Sponsored by Facebook - Trump, GOP allies prepare for SCOTUS nomination this week Trump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court MORE (D).

Blankenship has increasingly lashed out at McConnell, suggesting he believes the GOP leader is behind the effort to sink his candidacy.

"My run for the U.S. Senate offers voters an opportunity to begin draining the Swamp—this is why McConnell and the establishment are spending millions to defeat me," Blankenship said in a recent statement.