By ~1990/1991, when the GOP had won three consecutive presidential elections and Bush was riding high on Gulf War glory, people were talking about the GOP's insurmountable lock on the presidency.
Then again, the GOP would take back the House in 1994, and I would argue they were the more powerful party from 1994 to 2006. Clearly there are people who are going overboard on the demographics-is-destiny argument, but I do think there's some truth to the idea that the GOP is currently at a long-term disadvantage.
Anyway, responding to the OP, The Emerging Democratic Majority (2002) was, as far as I know, the first prominent book predicting the current long-term GOP demographic issues. I think the general GOP response today is: a)the GOP can continue to increase its share of the white vote, b)GOP troubles with Hispanics are overstated, and c)minority turnout will decline after Obama leaves office. Sean Trende is the most prominent conservative-leaning political demographics analyst that I know of. As for the 2012 election itself, I think many Republicans/conservatives were somewhat blinded by their dislike of Obama; they thought he was doing so poorly in office that they didn't understand how he could win re-election, polls and demographics be damned.
