It’s a festive time: singing on the sidewalks, good cheer erupting at home and the office. I’m of course referring to the revelry that descends on the library carrels and fluorescently iridescent cubicles around Washington when the census data comes out.

Particularly giddy these days are the Republicans who’ve picked up a few more seats in Congress and a few more electoral votes for the presidential election, thanks to the demographic tide pulling out of the economically stagnant East and Midwest and moving toward the more vibrant South and West. (Note that this trend stops at the eastern California border, as that state, as well as Oregon and Washington, suffer from the Americanized version of what we used to call “Eurosclerosis.”)

Add in the fact that the GOP benefited from what might be called a 100-year flood of state legislative victories in the midterm elections that will translate into a bonanza of congressional redistricting pickups, and you can understand why the folks at the RNC are hitting the eggnog and photocopying their nethers with celebratory abandon.

I hate to be the wet blanket, like the guy at the office party who insists we all get back to work, or the boss who says your Christmas bonus will come in the form of a UNICEF donation in your name, but let’s not get carried away.

For starters, the political effects of the census are disproportionate to the actual demographic trends the GOP faces. For instance, one of the reasons why Texas and other Southwestern states are gaining congressional districts is that they are making huge strides in Hispanic-American populations, which doesn’t necessarily equal Republican votes.

More broadly, the core Democratic coalition of minorities, secular suburbanites, single mothers and people dependent on the government for their jobs is growing. The core Republican coalition of culturally or religiously conservative whites is comparatively shrinking.

So is GOP support in the all-important suburbs. As American Enterprise Institute scholar Henry Olsen notes, John McCain lost all of the suburban counties surrounding New York, Philadelphia, Chicago, Detroit and Boston, as well as the majority of St. Louis and Cleveland suburbs. With the exception of Orange County – where he got record-low support for any Republican – he lost all of Southern California’s suburban areas.

Contrary to a slew of misconceptions, the GOP isn’t even the party of the rich anymore. Nineteen of the 20 richest ZIP codes in the country gave much – much – more money to Democrats in 2008.

Now, of course, some of these trends tacked back the other way in 2010 (although midterm elections skew older and whiter than presidential elections). For instance, Republicans closed the gender gap – the Democrats’ historic advantage with women – for the first time since such exit polling began in 1982. Independents, who were key to Obama’s victory, gave the GOP a surprise second chance.

But that’s the point. In politics, demography needn’t be destiny. It’s more like a wind you can sail into or with, making your job easier or harder, but it need not determine your destination. By the way, isn’t there something vaguely racist about the idea that, say, blacks will always vote liberal because, you know, that’s what black people do?

The fraying of the Obama coalition wasn’t a function of demography but a result of events (including, crucially, Obama’s own decisions) and the debate those events produced. Now, Obama’s poll numbers are ticking up after a good December, and that, too, isn’t a matter of demography.

The only way for the GOP to make real progress toward becoming a majority party is by making and winning arguments. That’s true of all political parties, but some more than others. The Democratic Party is dedicated to transferring money from people and institutions it doesn’t like to people and institutions it does like. Since there will always be more “have-nots” than “haves,” that puts the GOP at a disadvantage, which is why making persuasive arguments is so much more essential for conservatism than it is for liberalism, and why coasting on short-term demographic advantages is so much more dangerous.

If you do a straight-line projection from today and assume that everyone’s politics hold constant, the GOP will be in big trouble, if not doomed, a generation from now. And that’s why, after the celebrations are done and the hangover has worn off, the Right needs to get to work explaining why they’re right.

© 2010 Tribune Media Services, Inc.