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Certain quarters have been deeply unhappy with Bridges' leadership for some time but not enough to get any real momentum behind a challenge - that all changed with the disastrous poll on Monday, with National's support diving 12 points, to levels not seen since the early 2000s.
Until now the party vote under Bridges had held up well but he's been dogged by low personal ratings. MPs have told RNZ they haven't seen the party's internal polling for some months and believe they've been withheld because they have not been good for Bridges for some time.
Senior MP Judith Collins has confirmed she will not be contesting the leadership; no doubt she weighed the likelihood of being able to pull off a win at the election that'll be held four months from now, almost to the day. Political leaders do not get to stick around long after election defeats and Collins has been around long enough to see exactly how that plays out.
The only real game in town is Bay of Plenty MP Todd Muller with Nikki Kaye, MP for Auckland Central, as deputy on the ticket.
They'd been doing the numbers as the caucus had become increasingly unhappy but it's understood they had not issued a formal challenge.
A major motivating factor from this week's poll is under those numbers up to 16 MPs could lose their seats, many of them in marginal seats or in list positions - some of the list places are held by National frontbenchers. A key strength of National in opposition has been its sheer size as the largest caucus in Parliament, affording it plenty of resources in both MPs to take on the government and the funding that comes with it.
Both National and, more recently, Labour have had their caucus decimated after dismal election results and not only does it destroy morale, but having the knife taken to funding, votes in the House, and all of the other aspects of parliamentary life makes the road to recovery that much harder.
It's all on - each side will now be looking to get solid votes - signed and sealed - before they front to caucus on Tuesday.