Over the weekend Donald Trump raged against the Russia “witch hunt,” which he claimed was an effort to distract from his push for “historic Tax Cuts & Reform.” And there actually is a relationship — but it goes in the other direction. If Trump survives this crisis — which may mean that American democracy doesn’t — tax cuts will have a lot to do with it.

For Republicans in Congress know perfectly well that Trump is utterly unfit for office and has been abusing his position for personal gain. Many of them surely suspected, long before Monday’s indictments, that members of his inner circle, and perhaps he himself, have colluded with a hostile foreign power.

If they nonetheless circle the wagons around Trump — in particular, if they allow him to fire Robert Mueller, which now seems all too likely — there will be one main reason: Trump offers their big opportunity to cut taxes for the very wealthy. Indeed, the nonpartisan Tax Policy Center estimates that almost 80 percent of the Trump tax cut would go to people with incomes over $1 million; these people would get an average cut of around $230,000 a year.

But here’s what gets me: The wealthy donors for whom the G.O.P. will apparently do anything, up to and including covering up for possible treason, will get no joy from their tax cuts.