The Daily Telegraph has an article about an opinion poll which points to a fairly significant upsurge in popular support for the Spanish monarchy in the days following the King's announcement of his intention of abdicating in favour of the Prince of Asturias. The article , which has some other relevant links, including one with comments from the King that he did not wish his son to grow too old waiting to succeed to the throne, can be seen at Was King Juan Carlos right to abdicate?
The suggestion may well be that in terms of serving the long term interests of the monarchy and the nation it has been the right, or appropriate, decision by King Juan Carlos. The King has shown himself a shrewd operator of the royal office since 1975, and this decision doubtless need to be understood in that light.
That said, it is unfair to all that he has achieved as King that recent difficulties should be seen to lead to abdication. It is also unwise that monarchs become, or are perceived to be, dependent upon popular support as reflected in such ephemeral things as public opinion polls. I am sure there are far deeper levels of support for the institution as well as the personalities of the Spanish monarchy, and that those will stand the future King Felipe VI in good stead.