Private polling isn't always superior to public and media polling, as the Washington Post's Jon Cohen writes in a smart piece slated for Sunday's Outlook section. But there are reasons why the polls conducted for campaigns may once again be superior in a state like Nevada, where the demographic makeup of the electorate is evolving quickly. Hispanics make up an increasing percentage of the Nevada electorate. In 2004, they made up 10 percent of the electorate, according to exit polls, and that rose to 15 percent in 2008. In 2010, Hispanics ticked up a percentage point as a share of the Nevada electorate, to 16 percent, despite a nationwide decline of a percentage point, back to 2006 levels. In 2006, Hispanics made up 12 percent of Nevada electorate. Furthermore, as a new report on Friday underscores, Nevadans are increasingly more difficult to reach in phone polls. Nearly 35 percent of Nevada adults in 2011 lived in households that only have a cell phone, whereas most public polls in this year's presidential and Senate races call exclusively or mostly landlines. And the rapid rate of landline abandonment -- fewer than 28 percent of Nevadans were cell-only in 2010 -- suggests that polls that ignore or undersample cell phones this year could suffer from increasing bias. And, as Ralston writes, the Democratic registration advantage in populous Clark County is expected to be even larger this year than in 2008. That makes overcoming Obama's 12-point margin of victory in 2008 -- or Reid's 6-point win in 2010 -- a daunting proposition for Republicans. The combination of demographic changes and the changing way Americans communicate with one another makes this election a difficult test for public election polling, and Nevada may represent its most challenging arena.