Being a political junkie, I get a kick out of maps depicting the electoral college results for past presidential elections. Going through recent history, we can see some embarrassing blowouts--FDR's 1936 rout of Alf Landon, Richard Nixon's 1972 shellacking of George McGovern, and Ronald Reagan's 1984 defenestration of Walter Mondale stand out specifically. Such lopsided victories seem very far away from today's electoral vote map--where for the past several elections in a row most states were "off the table" and the real contest comes down to less than a dozen.
Also notable was the strength the GOP used to have in the northeast and west coast--the Republican ticket never lost California with Nixon on either part of the ballot, for example, and Reagan managed to win states like New York and Massachusetts twice. The only states that liberal Democratic nominee Adlai Stevenson won against Eisenhower in both '52 and '56 were located in the deep south. The geographic and demographic nature of presidential election strategy during the Cold War years was alien to what it is now, where Republicans count on a base in the south, Rockies and plains states and try to cobble a bit more to eke out a close victory, and the Democrats count on the remainder.
Much of this has to do with the changes beginning in the 1960s, where the Democrats' embrace of civil rights helped shift the formerly single-party south (the single-party being the Democratic party) to the GOP, and the rise of "culture war" politics in the 1970s--particularly abortion politics post Roe v. Wade--that solidified the rural and southern states in the Republican camp. This shift also had the effect of losing the large numbers of secularist urban and suburban voters that used to be Republicans, as well as driving the black vote deep into the Democratic camp (the GOP did fairly well with the black vote prior to this shift). Thus, California, New York, Illinois and Pennsylvania--four big states that once were reliable targets for the Republicans--are regular locks for the Democrats.
In recent cycles, this new dynamic hasn't necessarily been fatal to the GOP--they've been able to cobble together the states they needed twice since 1992, though just barely--but I expect this to become a bigger problem for them in the next few cycles barring any major change. The bigger states that the Republicans count on--Texas, Georgia, and Florida--are seeing a growing population of Democrat-leaning immigrants and secularist professionals in their urban areas. It's not hard to imagine that those states gradually come within reach of the Democrats. When the GOP has to fight to keep Texas, they're screwed.
That said, you can't really expect nothing to change. The makeup of the two parties changes as new generations take over, and as politics adjust to new situations. The Democratic party of the 1950s--a cobbling of big-city ethnics, union members, farmers and southern conservatives as well as northeastern liberals--is a far cry from the party that is re-nominating Barack Obama in a few weeks. And the GOP that used to not bother trying to win Alabama and could win a majority of the female vote is quite different from the one meeting next week to nominate Mitt Romney.