Story highlights Sen. Susan Collins said Clinton lawyer Marc Elias should be recalled to the Senate intelligence committee

Collins said John Podesta and Debbie Wasserman Schultz should be recalled as well

Washington (CNN) Sen. Susan Collins said Sunday that the Senate intelligence committee should bring senior Democratic Party operatives back for testimony after revelations about the party paying intelligence firm Fusion GPS for opposition research on Donald Trump last year.

Some of that research became the now-infamous dossier of allegations about the now-President and Russia.

In closed-door meetings with congressional Russia investigators in recent weeks, Clinton campaign chairman John Podesta and former Democratic National Committee chairwoman Debbie Wasserman Schultz denied knowing who funded Fusion's opposition research, three sources familiar with the matter told CNN last week

"They absolutely need to be recalled," the Maine Republican said on CBS's "Face the Nation." "It's difficult to imagine that a campaign chairman, that the head of the DNC would not know of an expenditure of this magnitude and significance, but perhaps there's something more going on here."

A source familiar with the matter told CNN on Tuesday that the law firm Perkins Coie, as part of its representation of the Clinton campaign and the DNC, retained Fusion GPS and entered "into an engagement for research services that began in April 2016 and concluded before the election in early November."

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