The more the academics and analysts explore the entrails of last month’s election, the clearer and simpler the lesson becomes. As the Clinton folks might put it, “it’s the partisanship, stupid.”

Democrats did a first-class job of mobilizing their supporters and bringing them to the polls. But Republicans did an even better job, and that is essentially why they won.

The anatomy of the Nov. 2 voting is intriguing in itself, but its implications for the future of politics and government are even more important. It signals a protracted period of two-party competition and means Republicans and Democrats alike will face intense pressure to keep their coalitions intact.

Democrats, who came out on the short end of the 51-48 percent presidential popular vote and lost seats for the second election in a row in both the House and Senate, cannot afford any more defections. Losses among women, minorities and what remains of their Southern base would make the task of a comeback all the more difficult.

It surely was not a coincidence that President Bush began taking steps to split that Democratic coalition with his very first appointments to his second-term administration: Condoleezza Rice, a black woman with Southern roots and a California connection, to run the State Department; Margaret Spellings, another woman and a Texan, to run the Department of Education; and two high-profile Hispanics, Alberto Gonzales and Carlos Gutierrez, to lead the Justice and Commerce departments respectively.

But it is not only Democrats who have to worry about coalition maintenance. Republicans, and Bush in particular, are equally dependent on keeping the flock intact. Bush did not beat John Kerry among independents. Kerry won almost nine out of 10 Democratic votes and prevailed narrowly among independents. Bush won only by turning out massive numbers of Republicans and capturing more than nine out of 10 of their votes.

What was true of Kerry and Bush applied almost equally to the races for the Senate, the House and governorships. If you want to understand why House Speaker Dennis Hastert was so reluctant to split the Republican conference on the issue of intelligence system reform that he pulled the bill off the floor, the answer lies in this pattern of intense partisanship in the election returns.

House Republican candidates received more than eight of 10 Republican votes, while Democratic candidates received three of four Democratic votes. It was not surprising Hastert did not want to let Democratic lawmakers pass the president’s intelligence reorganization plan over the opposition of many Republicans. To do so would alienate him from his flock, and perhaps put some of them at risk with their voters.

All of this is a far cry from the pattern of government and politics with which we became familiar during the Cold War. As John Kenneth White of Catholic University points out in one of the clearest and most succinct of the many post-election analyses that have crossed my desk, from 1952 through 1988, Republicans won the White House seven of 10 times, but rarely were able to disturb Democratic control of Congress.

From Dwight Eisenhower through the first President Bush, the voting public generally trusted Republicans to manage international affairs, keep the communists at bay, assure a strong defense and run the economy. Democrats in Congress were preferred to look after the down-home concerns, such as Social Security, Medicare, education and the rest.

But that pattern of divided government has been decisively broken, and the ticket-splitting that facilitated it has become much less frequent. Part of the story is the change in the South, where conservative Democrats once prevailed. Now, their House and Senate seats are occupied by Republicans, and the region voted overwhelmingly for Bush in both his campaigns.

But partisans on both sides in other regions also are recognizing the genuine differences between Republicans and Democrats and choosing sides accordingly. Some of those differences are ideological. Some are cultural, including the issues of faith and religion, which drew so much attention in the immediate aftermath of the election.

But the overwhelming factor, the one that ties it all together, is the simple pull of partisan allegiance — the hold that each of the parties exerts on its own followers.

Where there is strong partisanship in the electorate, White reminds us, we are likely to see partisanship in government as well. “The significance of party to the 2004 vote means that compromise between the two parties-in-government is unlikely,” he writes.

Keep that in mind when the next Congress begins.

— David Broder is a syndicated columnist with Washington Post Writers Group.