What we know and don't know about the Trump-Russia dossier

The former British spy compiled dozens of reports detailing what he heard from his contacts

How did American intelligence officials come to brief President Obama, President-elect Donald J. Trump and lawmakers about supposed Russian plans to try to blackmail Trump? There are far more questions than answers. But here is a look at the story so far.

What we know

• Last year, a Washington political research firm, paid by Trump’s Republican rivals, hired a retired British intelligence officer to investigate the candidate’s ties to Russia.

• After it became clear that Trump would be the Republican nominee, Democratic clients began to pay the firm for this same “opposition research,” standard practice in politics.

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