PM won't be able to carry on walking this tightrope indefinitely
Theresa May is now living permanently on a political tightrope. Her long-awaited proposals for a new EU-UK trade structure post-Brexit in April 2019, published last Thursday, have been greeted by a polite silence by EU negotiators in Brussels.
But the accepted view in the EU capital is that she will have to move a long way further on before any real tangling can begin.
Back in London, her more moderate Brexiteer colleagues have that sinking feeling that she is already on the verge of what is acceptable to them. Further moves towards Brussels's view of things will demolish their fragile tolerance.
On the other side of the equation, party members who fervently wanted the UK to stay in the EU have now morphed into demanding the "softest Brexit possible", keeping Britain within the EU customs union, and as close as possible to the single market.
There are many practical examples of how she is torn in these various directions. Yesterday, she bowed to pressure from Brexit supporters in her Conservative Party, accepting four of their demands for changes to a customs bill, another key law which will underpin the EU-UK divorce arrangement.
The four amendments are significant. One of them could stop the UK from collecting tariffs for the EU, which was part of Mrs May's plan launched last week, unless the rest of the EU states do the same for London.
Another amendment could have big implications for Ireland. It makes the EU's "backstop" on customs impossible by ruling out a border in the Irish Sea.
The final two amendments would keep the UK outside the EU VAT regime, and also require specific legislation for the London government to form a future EU-UK customs union.
The prime minister lost her party's majority at an ill-judged election last summer. Her problems are compounded by dependence on the Democratic Unionist Party in the North, which is demanding the same Brexit as England, Scotland and Wales.
This acceptance of the four Eurosceptic amendments looks like a white flag. But her officials reject that assessment of things. They argued that these changes effectively put existing government policy into law.
The Brexiteers claimed it as a win. They also hope, perhaps quite rightly, that it will make Mrs May's plan less acceptable to Brussels.
Mrs May denied suggestions in Westminster that her Brexit plan was effectively dead. Her spokesman said accepting the amendments was "consistent" with the white paper policy document her ministers endorsed last week.
But the tricky part is explaining a reciprocal collection of UK and EU tariffs by Britain and the other EU states. Those close to the talks process wonder how London can make such demands on the other member states.
But this battle over the amendments to the Taxation (Cross-border Trade) Bill, or customs bill, is just one of many travails facing Mrs May as she continues a series of political tightrope walks.
Last week, she had to fight hard for the endorsement of her cabinet ministers. That was promptly undermined by the resignations of her Brexit secretary, David Davis, and foreign secretary, Boris Johnson.
The chorus of accusations of "betrayal" by ardent Brexiteers continues apace. On the other side of the equation, the Tory "soft Brexiteers" refuse to lie down, and one of their number, the former education minister Justine Greening yesterday called for a second referendum.
Mrs May's spokesman said there would be no second referendum under any circumstances. But for now the greater momentum is with the ultra-Brexiteers.
Increasingly, it looks like Mrs May cannot get a majority in her parliament for any likely outcome. Not for a "soft Brexit" - nor even for "crashing out" of the EU without a deal, something which could be catastrophic for many, not least Ireland.
The British Labour Party is likely to continue sitting on its hands throughout all this trauma. That party's overall view of Brexit remains equally unclear.
But it is at least very clear that Labour will do nothing to avert the collapse of Mrs May's government and an election this autumn. The chaotic events at Westminster appear to make this increasingly likely.
No political leader can walk a tightrope indefinitely and Mrs May has too many factors against her. The big question now is: how long can she continue? Few will be surprised if one day soon, she announces she is quitting.