A story of a small-town city council puts Paul Ryan’s shift on Donald Trump in perspective.

A friend of mine who lived in a small country town was elected to the local council. Because he is something of a gadfly, his colleagues made him speaker of the council, thinking that by promoting him to a largely ceremonial role, they were taming him.

He made one change: he had the council building lock its side entrances, so that the only entry was through the front, and made council members clock in and out like other municipal employees. They were livid — and the public was delighted.

The speaker of any deliberative body is a potentially powerful position, but has only one real weapon: the rules. (In Isaiah Berlin’s terms, if some politicians are foxes who know many things, and others are hedgehogs who know only one thing, an effective speaker is a hedgehog.)

Certainly, speakers can develop other tools — intellectual, political, and financial — but without the rules, a speaker is impotent.

Paul Ryan laid down the rules in January: as the likely chair of the Republican National Convention, he would support the party’s nominee, Trump included. That was long after Trump had announced his plans to suspend Muslim immigration, to which Ryan had objected. It was also long after Trump had made controversial remarks about Fox News anchor Megyn Kelly and after he had attacked his rivals for weeks, even bringing up Sen. Ted Cruz’s Canadian birth.

That was the appropriate time to stipulate, as Ryan did to CNN’s Jake Tapper last week, that “you have to unify all wings of the Republican Party in a conservative movement” before qualifying for the nomination. That new requirement effectively gives Trump’s die-hard critics a veto. It also represents a subtle yet “seismic” change in the rules Ryan himself established.

That is why, whatever the result of the Ryan-Trump talks this week, or the fate of Ryan’s primary challenger, Ryan has, for now, weakened his speakership.