Story highlights Trump is referring to an opposition research document that was compiled on him

The dossier has become an explosive political issue

Washington (CNN) President Donald Trump, keeping up his attacks on Hillary Clinton, suggested Thursday that his 2016 election opponent and her fellow Democrats could have paid Russians for dirt on him during the campaign.

"Disproven and paid for by Democrats 'Dossier used to spy on Trump Campaign. Did FBI use Intel tool to influence the Election?' @foxandfriends," Trump tweeted before dawn, adding, "Did Dems or Clinton also pay Russians? Where are hidden and smashed DNC servers? Where are Crooked Hillary Emails? What a mess!"

Disproven and paid for by Democrats "Dossier used to spy on Trump Campaign. Did FBI use Intel tool to influence the Election?" @foxandfriends Did Dems or Clinton also pay Russians? Where are hidden and smashed DNC servers? Where are Crooked Hillary Emails? What a mess! — Donald J. Trump (@realDonaldTrump) January 11, 2018

Trump is referring to an opposition research document that was compiled on him during the election, and it includes unverified allegations that the Russian government has compromising personal and financial information about the President.

The dossier -- because of its allegations and questions surrounding its origin -- has become an explosive political issue. Fusion GPS' efforts researching Trump were first funded by his Republican foes during the primary campaign. The law firm for Clinton's campaign and the Democratic National Committee picked up the tab once Trump became the clear favorite to win the nomination. After that switch, Fusion GPS hired a former British spy to put together the dossier on Trump's ties to Russia.

Trump has frequently criticized his own Justice Department over its handling of the investigation into Clinton's email use as secretary of state.

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