By Edward Hadas
The author is a Reuters Breakingviews columnist. The opinions expressed are his own.
Outsider parties are disrupting the political system in many developed economies. Greece is leading the way, with Syriza’s victory in the Jan. 25 election on a platform of radical economic change. Spain, where the new Podemos party leads the polls, could follow later this year. Fringe movements are also gaining traction in France, Italy and the UK. Something similar is happening even in the United States, where the Tea Party movement is shaking things up from within one of the established parties.