Why are Democrats protecting the Beltway smear-specialist firm Fusion GPS? Specifically, why are the party’s senators supporting Fusion chief Glenn Simpson in his refusal to say who paid to get that infamous President Trump-smearing “Russian dossier” drawn up?

As The Wall Street Journal’s Kimberly A. Strassel notes, Dem senators even passed on the chance to publicly question Jared Kushner and former Trump campaign manager Paul Manafort, rather than also expose Simpson to public questioning.

Maybe Democrats simply didn’t want anything to mess up their “collusion” narrative. Or perhaps they fear their own party used Fusion to commission the hit.

She’s not the only one on the case. Writing at Tablet, the Hudson Institute’s Lee Smith notes that perhaps the “dossier” was another Russian effort to interfere in US politics — an anti-Trump one to match Moscow’s work to undermine Hillary Clinton.

Because, Smith reminds us, “the point of the Kremlin’s assault on the American election of 2016 was to defame both candidates, and sow chaos, and thereby to discredit the American system of government, which rests on the consent of the governed.”

Fabricating such dossiers looks to be a Fusion specialty. Smith and Strassel both point to the Senate testimony of Bill Browder and Thor Halvorssen, each claiming to have been targeted by a Fusion dossier.

Browder was a force behind passage of the Magnitsky Act, a sanctions law that hits hard at Vladimir Putin’s inner circle and which Fusion was hired to help fight. Halvorssen is a human-rights activist (and occasional Post-Opinion contributor) who was publicizing corrupt maneuvers by Derwick Associates, a Venezuelan firm with deep ties to the Chavez regime that had partnered with Putin cronies.

As Smith notes, it’s not just Democrats in Congress who have reason to shield Fusion. The outfit has been feeding stories to the Beltway press for years, so reporting honestly on it would require “lifting the lid on the incompetence and malfeasance of their own institutions and colleagues.”

From the start, we’ve supported every effort to get to the bottom of Russia’s interference in the 2016 campaign. Will Fusion’s role in that meddling go ignored because of Democrats’ partisan interests, and the omerta of the DC press corps?