The first thing that most people associate with Nevada is Vegas. About 70 percent of the population lives in Clark County, home to Las Vegas and the surrounding metro area. In 2008, Barack Obama won the county by nearly 20 percentage points. But Nevada's primary contest is closed, meaning only registered Republicans can vote. In 2008, about 50 percent of the Republican caucus goers were from outside of Clark County. And, most importantly for Romney, roughly 1 in 5 were Mormons, who voted 9 in 10 for Romney.
Mormons are 74 percent Republican and they have proven extremely loyal in voting for Romney, who is a leader in the Church. Thus, even relatively small Mormon populations loom large in the Republican primary, as most Mormons are Republican, they have a high voting rate, and are extremely likely to support Romney as a block: