Come and have a go if you think you're hard enough.
Boil it down and that's what Sir Keir Starmer said to the cabinet today, at the start of what was - let's remember - just its standard weekly scheduled meeting.
The prime minister's message was spoken to a full meeting of 28 cabinet ministers.
But it was directed at one person present: Wes Streeting, the health secretary.
Streeting has been clear with the prime minister for months that he is ready for a leadership contest should one take place. But he has also been adamant that he would not be the person to trigger one.
As of first thing this morning, that remained his plan.
Then the prime minister made his bold gambit, taking refuge in Labour Party rules.
The Conservative system for displacing a leader, with which we all became so familiar in recent years, operates on the basis of whether MPs do or do not retain confidence in their boss.
The Labour system is different. For Sir Keir to be dislodged, 81 MPs would have to back a specific opponent to face off against him.
There are clearly well north of 81 Labour MPs who want the prime minister out. But the prime minister is cannily exploiting the divisions among them.
Some want a slower leadership contest because they support Andy Burnham who is not currently an MP. Others want the prime minister out now because they back Streeting.
So, will Streeting go for it? He did not rise to the prime minister's bait at the cabinet meeting. I'm told he took part in the scheduled discussion about the impact of conflict in the Middle East on the British economy.
Indeed, it sounds like there barely was a discussion about the leadership.
The prime minister delivered his opening statement and then the conversation moved on very quickly to its planned discussion subject.
Streeting tried to see Sir Keir afterwards to discuss his leadership but was rebuffed.
Regardless, a large group of ministers emerged quickly and were very supportive of the PM. It's being widely noted, too, that they included Business Secretary Peter Kyle and Science Secretary Liz Kendall, ministers who are seen as ideologically and personally close to Streeting.
But the PM's defiant strategy was almost immediately challenged by the resignation of a high-profile minister, Jess Phillips, followed shortly by that of her ministerial colleague Alex Davies-Jones. And sources are telling the BBC that more will go this afternoon.
This drumbeat of resignations is awkward for the prime minister, making plain that his gambit this morning has not quelled the frustration in parts of his government.
It recalls the way in which Boris Johnson was ousted by a flood of resignations from his ministers.
But that included cabinet ministers right up to the chancellor. This is a trickle, and the prime minister is a long way off the situation Johnson found himself in where it was genuinely hard to see how he could form a government.
So what happens next?
Beyond the question of what Streeting does, there is the question of what the 'soft left' of Labour does - which is broadly the group of the PM's critics who back Burnham. Allies of Streeting say that it is this Labour faction which initiated this leadership crisis with co-ordinated calls for the prime minister to set out a timetable for his departure.
It was intriguing that Ed Miliband, the energy secretary, did not say anything as he left cabinet. He is politically close to Miatta Fahnbulleh, who quit as a government minister first thing this morning and called on the prime minister to consider his position. She is backing Burnham, and it will be interesting to see if other ministers of her persuasion follow her lead.
Burnham's supporters have said for days that he has a path back into parliament, which is to say an MP willing to vacate their seat potentially enabling him to fight a by-election.
If there was an ideal time for Burnham, who has been spotted in London today, to make good on that promise it was surely yesterday. Today would work nicely too.
Otherwise it may be that those on this wing of the Labour Party begin to seek a different candidate who is currently an MP.
One other element of Labour's rules to remember. If somebody were to challenge Sir Keir directly, then the prime minister does not need to solicit 81 nominations of his own: he would automatically be on the ballot of Labour members.
A senior government source suggested to me today that one possibility here is that Sir Keir defeats Streeting in a leadership contest, with the prime minister receiving the support of MPs who want him out - but not to be replaced by Streeting and therefore not yet.
There are all sorts of permutations which are plausible from here.
And with a daring display of prime ministerial authority along with a big dose of political stubbornness, Sir Keir has kept an awful lot of those options on the table for now at least.
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