As Sean Trende has pointed out, it relies on a selective reading of the evidence — emphasizing 2012, 2008 and 2006 but ignoring 2014, 2010, and 2004.14 and 10 are midterms, when the emerging demographic nightmare for the GOP stayed home. 2004 was way back on the demographic curve, and it was a warmongering year when the GOP used gay marriage as a wedge to get their voters out. And even then, Bush barely won.
Perhaps more important, predictions made on the premise of “emerging” majorities have a miserable track record: Republicans were bragging about their “permanent” majority in 2004, for instance, only to get their butts kicked in 2006 and 2008.
|From Pew Research Center|
However, this still ignores the surge in minority voters, especially Latinos, and especially in swing states, or previously red states like AZ that will gradually turn blue as long as Republicans keep hating on minorities.
And this is the important part. The sliver of the GOP that wants immigration reform, or sentencing reform, or any other logical "outreach" to minorities will be crushed by the xenophobic base that votes in primaries.
It's a real problem for them, and to shrug it off with such a condescending brush off reveals a lack of understanding of the facts behind the actual demographic theory.
So, comparing Democratic claims of an emerging majority to Republican claims isn't really fair. The GOP was bullshitting. They had nothing to base their claims of an emerging majority on. Democrats actually do. See the original book on the subject, The Emerging Democratic Majority, by John Judis and Ruy Teixeira.
But, hey, Nate, at least we can bet on it at Predict It, where a Democrat is currently a 56% favorite to win the White House.