The Gillard government's immediate reaction to the departure of the Greens leader Bob Brown and to his replacement by Christine Milne was one of concern.
Since the balance-of-power alliance with the Greens that was imposed on it by the hung parliament, Labor has haemorrhaged political support.
Firstly, the arrangement resulted in Labor putting a price on carbon, which exposed Julia Gillard to the extremely damaging claim she had broken her election promise regarding no carbon tax.
Secondly, Labor wins no support from the left for this policy or any other green measures. It just bleeds from both ends.
While the Coalition primary vote has become entrenched at or about the 44 per cent it received at the August 2010 election, Labor voters have deserted the government, with 10 per cent of those who voted Labor now opting for the Greens or parking their support in the ''undecided'' category.
Brown entered the Senate in 1996, the same year John Howard became prime minister. While poles apart politically, Howard and Brown were conviction politicians.
This underpinned Brown's success in building the Greens federally to the current peak of nine senators and one member of the lower house.
Brown's reward for conviction was best demonstrated at the 2001 election, which was dominated by the MV Tampa episode. Labor, under enormous pressure, acquiesced with Howard's hard line against the asylum seekers and went backwards. The Greens advanced.
Over the years, Brown also developed a degree of pragmatism. He talked a big game but, especially towards the end of his leadership, accepted that in politics, sometimes something was better than nothing. The greatest example was the watered-down mining tax, with which the Greens were unhappy.
''Our position is that ultimately we are going to have to pass the mining tax because Tony Abbott's Coalition is opposed to it,'' Brown said.
This position caused some frustration within the party given the Greens' ability in the Senate to toughen the mining tax. But Brown knew Gillard would not budge.
The worry inside Labor now is that Milne will not share that pragmatism.
One senior figure said the common view is that an alliance with a Milne-led Greens could damage the government more than the Brown alliance because of Milne's reputation as a policy hardliner and her uncompromising rhetoric.
It was known that Gillard could reason with Brown, saying: ''Bob, we've gone out of our way for the Greens on this issue, can you tone it down on that one?'' And at times, Brown would reply: ''No worries, leave it to me.''
Milne deserves to be given a chance before being judged. She has rejected the hardline tag and has promised a more open party. She has pledged, somewhat pointedly, to be a more consultative leader and stated that Brown's departure means the rest of the Greens team will now have a chance to ''shine''.
But Gillard's warning that she expects Milne and her party to ''conduct themselves responsibly and reasonably'', including letting the government return the budget to surplus, was deliberately sharp.
The first test of how much, if anything, has changed under Milne's tenure will be the Greens' response to the budget.
The government wants a 1 percentage point cut to company tax to be funded by the mining tax.
The Greens, including Brown, have so far refused to support this, saying they will allow the tax for small companies only - those with a turnover of less than $2 million.
They say bigger businesses should receive nothing and the money saved should be spent on worthy national projects such as a dental scheme.
Milne's opening statement as leader included attacking the mining industry as rapacious and the ''old economy''.
Milne believes the economy is approaching a tipping point between old and new, and wants to work with what she calls ''progressive business''. But to do one at the complete exclusion of the other, especially when the other is not yet ready to carry the economy, is obviously risky.
The last time the miners were written off as the ''old economy'' was at the start of last decade when all and sundry slammed Peter Costello for not pinning the economy to information technology by climbing aboard the dotcom boom.
As Costello noted in his memoirs, if Labor and others had had their way, ''we would have got out of mining just when it was about to take off and invested in technology just when it was about to collapse''.
Milne is on the record as demanding that the $2 billion diesel tax rebate the miners receive be cut back harder than the 6.2¢-per-litre reduction planned for the budget and she supports calls to pare back their other tax perks, such as accelerated depreciation.
It has been speculated that if the Greens were to support the company tax cuts in full, then they will demand in return the further reduction of the diesel rebate, which they believe should be phased out.
The government needs the Greens because the Coalition opposes the tax cut on account of the way it is funded.
The miners are angry and alarmed again. On Friday, before anyone knew Brown had quit, they published full-page ads warning the government not to accede to the demands of some ''groups still demanding Australian mining should pay even more''.
Ominously, they reignited the ''keep mining strong'' tagline - the same as in the $22 million anti-mining tax ad blitz that crippled Kevin Rudd's leadership and almost killed Labor.
Phillip Coorey is the Sydney Morning Herald's chief political correspondent.