Marco Rubio and Ted Cruz got their first real head-to-head skirmishes in the final debate of 2015, and still nobody set a glove on Donald Trump who holds commanding leads in the national polls. Tuesday night's debates didn't change much in the Power Rankings, but they probably cemented Rubio, Cruz, and Trump as the only three candidates with serious chances of winning the nomination. Jeb Bush's so-so performance can be seen as a missed opportunity to make himself relevant again, increasing the perception of Rubio as the strongest establishment candidate. Cruz held his own against Rubio, and dealt deftly with...