The Democratic party has long portrayed the Republicans as the party of old, greedy, out of touch, white men while they were the party that reflected America's diversity, youth, and vigor.
A more accurate assessment is that the Republican party is rapidly becoming, as Howard Dean noted, the white party. They are no longer the party of international restraint (sorry Dr. Paul, you are alone on that one) thanks in large part to Ronald Reagan, two George Bushes, and some Arab terrorists. They are no longer the party of constitutional government since abandoning those principles after Barry Goldwater's defeat in 1968. They certainly aren't the small government loving, libertarian leaning conservatives that Reagan hoped to galvanize. They aren't even the pro-business party anymore with the McCain-Palin ticket.
The Republican party is essentially Christian and white. Ron Paul and John McCain in the same party along with Rudy Giuliani, Tom Tancredo, Patrick Buchanan, and Sarah Palin? There is no cohesive political vision that holds that group together except for Christianity.
What does that make the Democrats though? Well, they are effectively the party of blacks and Catholic, non-Cuban hispanics, baby-boomers, and explicit socialists. The Democrats having been losing control over white women as a reliable voting block since Reagan and the question of abortion ruptured the feminist movement; they've nearly completely lost white and hispanic evangelicals; Unions are rapidly diminishing in influence and power; Free-trade issues and low taxes became winning issues and were co-opted by Clinton in 1992. The Democrats where losing political viability, and quickly.
Of course George W. Bush saved the day for the opposition party through his obscene incompetence and wild unpopularity. The Democrats had been given a new lease on life but how were they to remake themselves?
Their preferred method was to simply import voters by way of illegal immigration. That issue stalled (for now) and so they temporarily wandered in the dark with John Kerry's tired and vacuous run in 2004. Now in 2008 they have regrouped, reorganized, and recreated themselves by traveling back in time to 1968 with Barack Obama as the neo-Nixon figure.
Their 2008 platform reads like a history lesson on bad domestic ideas for the last seventy years. Tax the rich, massive regulations, huge government programs, etc. Barack Obama has capitalized on his racial-celebrity status to court the media, identity politics to build a base, rhetoric of change to court swing voters (his natural opponent was strangely enough Ron Paul - who actually had ideas), a wildly unpopular president with a wildly unpopular war to court the youth vote.
The Democrats don't have ideas and they don't want them, they want power, influence, but ultimately control which is the only thing leftists ever want. Republicans have abandoned their ideas for political expediency and have learned the cruel Randian lesson that if you sacrifice principle for practicality, you lose. Thus the future of American politics looks to be purely a demographic battle for dominance.