I don't usually dispense relationship advice in this column. But the adage about marriage is often true of politics: What is not said is more destructive than what is said.

For example, over the last 18 months the president has said and done a number of things that warranted dissent from Republicans — not just from party leaders, but from rank-and-file legislators, pundits and other commentators. But the dogs did not bark, opting to stay silent.

We need not take up too much space quibbling over specifics. All one need do is play the "What if Obama said this?" game to see that the moral arc of the GOP has bent toward President Donald Trump.

Then, a few weeks ago, the president proposed sweeping steel and aluminum tariffs and heaped praise on the benefits of trade wars. Suddenly, Congress and much of the conservative commentariat rose up in protest.

Trump's top economic adviser, Gary Cohn, who reportedly almost resigned last summer over the president's morally equivocating response to a neo-Nazi rally, apparently found tariffs a nobler hill to die on.

As a free-trader, I welcome this response. But just imagine you're a run-of-the-mill Democratic congressional candidate aiming to unseat a Republican who never spoke up about Trump's remark about African countries, the unfolding drama over Stormy Daniels, Trump's endorsement of Roy Moore, his attacks on the First Amendment or his flirtation with cutting off aid to hurricane-ravaged Puerto Rico because of a spat with the mayor of San Juan.

How easy it would be to say: "My opponent never objected to these things, but when Trump tried to save manufacturing jobs, he leapt to his feet to protest at the bidding of the same fat-cat free-traders and globalist big businesses that outsourced so many of your jobs. My opponent is OK with the president endorsing and campaigning for an accused child molester, but he will fight to the death to keep cheap Chinese steel from pouring into this country."

Yes, it's a dumb economic argument — steel tariffs would cost more American manufacturing jobs than they'd save — but it's a great political one.

This is just one illustration of the Republican dilemma. The president divides the right while he unifies the left. Praise Trump on his controversial statements and you risk alienating suburban Republicans, particularly women. Criticize Trump and you risk not only his wrath, but also the wrath of the portion of his base that demands rhetorical fealty to Trump in all things. Because this constituency has disproportionate influence in conservative media and GOP primaries, the safest course of action is often silence, or some clever dodge like, "I don't respond to tweets."

The GOP has created a kind of collective-action problem for itself. By making these individual decisions out of self-interest in the moment, the party as a whole ends up getting pulled in a direction not of its own choosing.

Voters don't judge parties on their lists of principles, but on their real-world priorities. Not objecting to something sends as clear a signal as objecting does. It's fun to listen to Republicans vent off the record, but most Americans don't get to hear any of that. They do hear the silence, however.

And so does Trump. Over the weekend, the president floated a fairly obvious trial balloon, tweeting, "The Mueller probe should never have been started," and calling it, in all caps, a "WITCH HUNT!"

It's not shocking that the president would want to fire special counsel Robert Mueller, but he has never attacked him directly before. The usual suspects cheered on Trump, while most of the party was silent.

One of the few exceptions was Sen. Lindsey Graham, who said firing Mueller would be the "beginning of the end of his presidency." House Speaker Paul Ryan offered a lackluster response through a spokesperson: "Mr. Mueller and his team should be able to do their job." Senate Majority Leader Mitch McConnell said ... nothing.

Off the record, Republicans often say they're afraid Trump responds to being told not to do something by doing it out of spite. That's a real concern. But it's not an excuse.

If Trump does fire Mueller and a constitutional crisis ensues, the previously silent, suddenly angry Republicans will be asked why they're speaking up now. That is, if they speak up at all.

Jonah Goldberg is a columnist for National Review. Email: goldbergcolumn@gmail.com

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