How much more does Donald Trump have to do before Republicans turn on him?

When Donald Trump won I argued that the Democrats should consider working with him in a limited number of areas, like spending more money on America’s roads and railways, to advance their own interests and help sow strife among Republicans. If that seems quaint now, it is because I was overestimating Trump’s ability to govern sensibly. By just a little.

No longer need we wonder what path Democrats will take. Resist, frustrate and foul up as comprehensively as possible would sum it up. Trump has earned their unflinching disdain by now. Moreover, the passion of grassroots opposition evidenced in huge marches all across the country – women, scientists, immigrants among them – means they can hardly do otherwise.

The far more urgent question now is about the intentions of top Republicans. What does Trump have to do to persuade them that the time has come to cut the cord. To put country before party. To realise that their own place in history might come not from trying to save a president who may already be beyond saving but from showing some guts and saying enough is enough.

Their reluctance to go there is appalling and also not hard to understand. Nowhere is the pressure more uncomfortable than for Paul Ryan, the Speaker of the House, and Senator Mitch McConnell, the majority leader in the upper chamber. So far, at least, these two have failed to show the slightest backbone in the face of Trump’s blunder machine. Lame, limp, craven.

“I think we could do with a little less drama from the White House on a lot of things,” McConnell told Bloomberg News in response to Trump Sin #152. I am not actually counting, but we are getting up there. This would be his Isis aviation-plot mouth fart in the company of, no less, Russia’s foreign minister and ambassador to the US in the Oval Office.

Look, none of this is easy on Republicans. They believe still that it is in their interest that this president succeeds. For that to happen, he has to have strength. That will require a long stretch without drama, as McConnell intimates. Only if the notion of Trump gradually making headway on his agenda takes hold will his approval ratings begin to tick up and his credibility recover.

Their power is now immense. Trump evinces swashbuckling independence that allegedly allows him not to care very much about anyone on Capitol Hill, the likes of McConnell and Ryan included. But that is now an illusion. The day they or any of the Republicans, particularly in the Senate, turn their backs on him is the day his presidency starts to come undone.

So how close are we to that point? How frightened of them should Trump be right now? In less than a week, we have had the bungled firing of FBI Director James Comey in the midst of the investigation into whether his campaign colluded with Russia’s efforts to subvert last year’s presidential election. And now we have this: a sitting president blabbing secrets to Russia, committing an act of treason, possibly. Committing an act of egregious foolishness, certainly.

First, the polls. Yes, he is burdened with an historically low approval rating, around the 40 per cent mark. But there is, as yet, little to indicate that the core base of Trump voters is fracturing. There are signs that some independent voters who were once willing to give him the benefit of the doubt are starting to drift away. That is a red flag for Republicans but not a storm warning.

The bomb dropped by The Washington Post of Trump blurting a vital intelligence secret to Sergei Lavrov last week triggered a quick pushback from the White House. But as was widely noted, those statements, notably one offered by HR McMaster, the National Security Adviser, to reporters outside, denied things that were never in the Post story in the first place. By morning time, Trump had, via Twitter, confirmed the main substance of the report. He had shared secret intelligence (but he didn’t think he’d done anything wrong).

With each new Trump debacle, so new levels of Republican disquiet reveal themselves. “Inappropriate,” was the word chosen (carefully) by Senator Richard Burr, chairman of the Senate Intelligence Committee, the day that Trump suggested on Twitter that Comey “better hope” there wasn’t any tape of the conversation the two of them had had over a dinner in January. The release by the Post of the intelligence-leak story earned a strikingly blunt critique of this White House from Republican Senator Bob Corker who leads the Senate Foreign Relations Committee. “Obviously, they are in a downward spiral right now and have got to figure out a way to come to grips with all that’s happening,” he said.

Whether you call it a blunder or something more sinister, Trump’s loose-lip moment with the Russians threatens to sound the sirens like never before among Republicans who had been nurturing the hope that at least on the national security front the White House had its act together. This is particularly the case for Lindsey Graham of South Carolina and John McCain, the former presidential candidate and now chair of the Armed Services Committee. Especially alarming to them will have been the sad spectacle of McMaster being thrown out to the press wolves to defend what looks like the indefensible.

McCain, like Graham, has so far been carefully calibrated in his criticisms of Trump. But he seemed like a man who had partially lost his footing when reporters caught him unawares within hours of The Washington Post report coming out. “I can’t comment on every breaking news story,” he was quoted as saying, before reflecting a little more on what information Trump may or may not have leaked. “That’s why it’s classified. They have a reason to classify it, OK? And when they say it’s classified, if it was public knowledge, then it could hurt the national security of the United States. That’s why we classify.” If the report was true it would be “disturbing”, he offered.

McCain is not always so measured and nothing is likely to infuriate him more than McMaster being forced to endanger his own reputation and effectiveness at the behest of a boss undeserving of such loyalty.

To imagine that he and his Republican colleagues are twiddling their thumbs as Trump careens from one calamity to another would be wrong. In private, they are letting the White House know full well of their despair. But standing up to Trump – really standing up to him, for country, never mind party – means doing it in public. And so far they have been unwilling to do that.