The reason both men were on the outer to begin with was the same: issues of trust. The given reason both were now back in the good books was also the same: the passage of time.
It seems Dunne's misdemeanours were just so 2013. Peters' dated back to 2008 and Key claimed that the public had re-elected him, therefore who was he to continue to hold a grudge?
He had, to steal former Prime Minister Helen Clark's phrase, "moved on". The real reason was more cynical - Key had no choice.
Having spent much of last year scoffing at Key for his lack of coalition partners, Opposition leader Cunliffe described Key as "desperate" for lining up five potentials. He took aim at the underlying cynicism in Key's decision to leave the option of working with Peters open and to welcome Dunne back despite obvious distrust issues with both.
Cunliffe ignored the fact he also had five potential coalition partners - the Greens, Mana, NZ First, the Maori Party and United Future.
Despite Dunne making it clear his preference was National, Cunliffe said he "would pick up the phone" if Peter Dunne rang him. He would also work with Mana's Hone Harawira, but said it was "extremely unlikely" he would make Harawira a minister.
There was little to lose for Key in setting out his options, despite having derided Labour in the past for being reliant on a similar multi-headed monster itself to form a coalition.
Both parties are facing a Goldilocks problem. Key's favoured coalition picks are too weak and might not make it at all. Labour's are too strong and leave it battling opponents' claims that it will be too easily pushed around in government by the demands of the juggernauts of the minor parties: the Green Party and NZ First.
All the harrumphing and guffawing that accompanied Key's actions were rather hollow. The public voted to keep MMP. MMP is a team sport - coalitions are part and parcel of it. The various permutations those coalitions might take are also pretty obvious.
Yet every election there are gasps of shock and horror when the major parties move to shore up their coalition partners with deals in electorates or warm overtures.
All Key has done is state the obvious. Even the NZ First issue came as no real shock, given Key has signalled his change in stance for the past two years.
The announcement has had one big advantage for Key - it has ensured he grabbed the momentum at the start of the year. That built on the king of all photo ops, his game of golf with Barack Obama. He is expected to build on it further today with his "state of the nation" address and an education policy announcement. Snatching the momentum from your opponent is a critical move for a governing party trying to avoid any perception it is tired while seeking a third term.
By way of returning serve, Cunliffe could only flail a weak lob over the net, announcing he was dropping two of Labour's 2011 policies which were borne from desperation and which both Cunliffe's predecessor, David Shearer, and Cunliffe had already indicated were on the chopping block.
Cunliffe has wisely held off on firing the big guns until Key is done. Instead, he will do his "state of the nation" - complete with shiny new policy - on Monday. That policy is expected to target lower income families and Cunliffe has also indicated the Super policy is up for change although it is unclear when those changes will be unveiled. When they are, it is likely to retain the ultimate goal of raising the age to 67 while introducing some flexibility for those who wish or need to retire earlier.
As for Peters, it is even possible that behind all the hissing and spitting he is quietly relieved Key is now pulling his pigtails, not least because a substantial bloc of his traditional support base was National-friendly voters. More importantly, he is restored to his favourite position as Parliament's equivalent of Helen of Troy being a-wooed by all comers. A rollicking ride awaits before we learn which suitor, if any, will overcome. Nobody can string out the rom-com storyline like Peters.
