It is easy to list what might go wrong in Europe in 2016: a global economic slowdown that rekindles fears over eurozone debt sustainability; a worsening refugee crisis that leads to the collapse of the Schengen passport-free travel zone; increased political instability as a result of rising support for populist parties; plus the possibility that the U.K. might vote to exit the EU in a referendum likely later this year, which would trigger a political earthquake that would destabilize the entire continent.

Less easy is to identify what might go right—what could happen in 2016 that might reverse the pervasive sense of impending doom. But one positive surprise could occur this weekend when Greece’s main opposition party, New Democracy, votes to choose its new leader.

This election pits veteran party insider Vagelis Meimarakis—who served as interim leader during September’s snap election, in which the party failed to increase its share of the vote—against Kyriakos Mitsotakis, a 47-year-old Harvard-educated free-market reformer who has campaigned for the leadership on a message of radical overhaul of both his party and his country. In the first round, Mr. Mitsotakis trailed Mr. Meimarakis by 27% to 40%. But in this weekend’s second round, Mr. Mitsotakis may yet come out on top after securing the support of two of his defeated rivals.

In many respects, Mr. Mitsotakis is an unlikely standard-bearer for uncompromising reform of Greece’s corrupt political and economic system. He is the son of a former prime minister, albeit one of the few precrisis prime ministers to attempt to grapple with Greece’s deep problems, and his elder sister is a former deputy party leader, leaving him vulnerable to the charge that he is just another dynastic politician. Critics also accuse him of lacking charisma and being a poor media performer.

But Mr. Mitsotakis was widely regarded as one of the most effective ministers in the previous government, winning respect from Greece’s creditors for his efforts to streamline the dysfunctional public administration and introduce new concepts such as promotion on merit. Meanwhile, his sister’s refusal to publicly endorse his candidacy, which is widely assumed to reflect her aspirations for her own politically ambitious son, could be said at least to show that Mr. Mitsotakis is his own man.