How do we get people to agree on a common set of facts?

[Statilius the Epicurean]

Time.

The only way a disagreement over basic facts can be resolved is when the two sets of facts collide with reality and one is proven the stronger.

In this country we had a very divisive EU referendum with the winning Leave campaign pushing a set of alternative facts: "£350m for the NHS if we leave", "German industry will lobby to get us a favourable deal", "the EU is on the verge of collapse anyway", "Europe needs us more than we need them because we buy their products", "the ROTW will be lining up to sign trade deals with us" etc. etc., beating out the facts of the Remain campaign. Anyway, this delusion was rampant among government ministers and a small majority of the public and is only beginning to slowly dissipate now that Brexit negotiations have begun and fantasy is crashing into reality.

So with Trump: if he really did collude with Russia, and if he really is as awful and incompetent as Democrats believe, then the only thing they can do is wait for this to be exposed by the investigation and Trump's agenda. Bush won two elections and his incompetence crashing into reality permanently discredited neoconservatives and "compassionate conservatism". So with Trump.