Since the 2004 elections, many liberals and Democrats have been debating "why Kerry lost" and, more broadly, "why the Democrats keep losing ground." Much of the debate has focused on the never-ending seesaw of "swing voters vs. base voters" or cultural/religious issues.

But what has been completely missing from the conversation is the fact that even when the Democrats win more votes than Republicans, they don't necessarily win more seats. That's true in the U.S. Senate, the U.S. House, and the Electoral College.

It turns out there is an unfair structural disadvantage embedded into our fundamental electoral institutions that makes it more difficult for Democrats to win than Republicans. It's like having a foot race in which one side begins 10 yards in front of the other, election after election.

This structural Republican advantage results from regional partisan demographics in Red vs. Blue America: Democrats increasingly dominate urban areas and the coasts, Republicans dominate most everything else. So look at what happens as a result of these demographics.

A recent study by the nonpartisan Center for Voting and Democracy shows that if Democrats and Republicans win exactly the same number of votes nationwide for elections to the U.S. House, Republicans end up winning about 50 more House districts than Democrats. It turns out there is a fundamental anti-urban (and thus anti-Democratic) bias with single-seat districts. The urban vote is more concentrated and so it's easier to pack Democratic voters into fewer districts.

As Democratic redistricting strategist Sam Hirsch has noted, nice square districts are, in effect, a Republican gerrymander because they "combine a decade-old but previously unnoticed Republican bias."

Here's the best-known recent example of this. Even though Al Gore won a half million more presidential votes nationwide than George Bush in 2000, Bush beat Gore in 47 more of the 2002 congressional districts. And that's up from a previous 19-seat edge, showing that trends are tilting Republican. The winner-take-all electoral system distorts representation and clearly gives Republicans an advantage, allowing them to win more than their fair share of seats. So the current Republican margin in the House of 232 to 203 -- only 29 seats -- is actually a decent showing for Democrats.

31 of 50 states in 2004, showing Democrats' near impossible battle to win a majority in the malapportioned Senate where each state, regardless of population size, has two U.S. Senators.

Professor Matthew Shugart from the University of California at San Diego says that, for the past three election cycles, more than 200 million votes were cast in races electing our 100 senators. Republicans won 46.8 percent of the votes in these elections -- not even close to a majority. The Democrats won 48.4 percent -- more votes than Republicans. Yet the GOP currently holds a lopsided 55 to 44 majority. In 2004, Democratic senatorial candidates won more than 51 percent of the votes cast, yet Republicans won 19 of 34 (56 percent) contested seats. In other words, the minority party has won the majority.

The 18th-century constitutional structure that gives every state, regardless of population size, two senators, has produced a pro-Republican bias that has warped representation not only in the last two elections but for decades. The GOP has been over-represented in the Senate in nearly every election since 1958, primarily due to Republican success in low-population, conservative states in the West and South. Not surprisingly, the Senate is perhaps the most unrepresentative body in the world (outside Britain's House of Lords), with not only Democrats under-represented but only five of 100 seats held by racial minorities and only fourteen held by women.

The Electoral College for presidential elections also gives an advantage to Republicans, largely for the same reason as the Senate -- low population states (which tend today to be conservative red states) have more electoral votes per capita than the rest of the nation.

So in the current climate of Red vs. Blue America, Democrats must overcome an 18th-century political system that puts urban-centered Democrats at a decided disadvantage. These structural barriers will undercut attempts by Democrats to gain control over the government, no matter how many volunteers Democrats mobilize or how much money they raise.

Surprisingly, given its significance, the Democratic Party seems to be blissfully unaware of this structural GOP advantage that is so hardwired into our basic electoral institutions. Karl Rove and Republican leaders must be cackling with glee, since it virtually ensures their control of the federal government for years to come.