The super PAC allied with Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE (R-Ky.) is launching its opening salvo against Democratic Sen. Claire McCaskill Claire Conner McCaskillDemocratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally Missouri county issues travel advisory for Lake of the Ozarks after Memorial Day parties MORE (Mo.) ahead of her 2018 reelection campaign by needling her over contact with Russia with a new nickname —"Comrade Claire."

The Senate Leadership Fund's first digital ad zeroes in on McCaskill's previous comments about the Russian ambassador. It's part of a broader campaign effort first reported by The Hill that will stretch through the election.

McCaskill tweeted back in March that she had never spoken to or met Russia's ambassador to the United States during her career in the Senate. The tweet responded to reports that Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsTrump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status White House officials voted by show of hands on 2018 family separations: report MORE failed to disclose meetings with then-Russian Ambassador Sergey Kislyak.

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Democrats were blasting Sessions at the time for the revelations in concert with the investigation in to Russia's meddling in the 2016 presidential election.

But soon after, tweets surfaced of her commenting on a 2013 meeting and a 2015 phone call with the ambassador. And CNN reported that McCaskill had attended a reception at Kislyak's house back in 2015.

McCaskill later argued that that she had meant she never met with him as part of her role on the Senate Armed Services Committee, on which both she and Sessions served together before his appointment to the Justice Department.

A Justice Department spokesperson had argued at the time that Sessions' meetings came as part of his service on the committee, an assertion Democrats openly questioned.

Senate Leadership Fund's video rehashes the controversy, complete with Russian music and imagery, pictures and news clippings from reporting surrounding the revelation.

The group's broader campaign tars McCaskill as "Millionaire Claire" on a new opposition research website meant to soften her up before her reelection bid.

The opening digital push costs about $5,000 and will be bolstered by other buys targeting McCaskill in the future.

McCaskill is expected to have one of the toughest reelection races of the cycle, thanks to President Trump's success in her state in November.

The Senate Leadership Fund is one of the top Republican outside groups in politics and is tasked with defending the Republican majority in the Senate.