The recent Democratic winning streak in presidential elections connects directly to the “youth advantage” enjoyed by Democratic candidates: the Democratic nominee has been younger than the GOP nominee in five of the last six of presidential contests, and the younger candidate each time won the popular vote.

The only GOP victory came in 2004 when John Kerry was three years older than his one-time Yale classmate, George W. Bush. Democrats have benefited consistently from an edge among younger voters: in 2012 Barack Obama beat Mitt Romney with those between ages 18 and 29 by an almost two-to-one margin, while Romney prevailed among the 81% who were 30 and above.

In 2016, however, all prominent Republican candidates are younger than Hillary Clinton who’ll be 69 by Election Day. If the GOP nominates a youthful conservative leader like Rubio, Walker, Cruz or Paul, Republicans could blunt a Democratic edge that’s helped them sweep recent presidential contests.