The congressional power shift in the 2006 elections only became possible because of another, less-noticed change: the Democratic Party's shift toward the center.

The Democrats became competitive, and then won, because the party reached out to the political center and the center of the country. The blogocracy, activist networks and bicoastal elites had limited relevance in an election largely fought and decided in the "flyover states." The electorate did not swing left; Democrats in swing seats met the voters in the center.

In fact, the campaign seems to have buried the notion that swing voters are a dying breed and that elections are won by mobilizing the base. Polls in key seats showed over 20 percent of voters up for grabs as late as 10 days out. This is a lesson neither party can ignore for 2008.

Tallies in September and on election eve showed the majority of battleground House seats were on neither coast. "Perhaps the most remarkable thing about this election is that Republicans are having to fight and spend money in states and districts where few Democrats have dared tread in recent years, like Idaho-01, Nebraska-03 and Nevada-02," wrote veteran commentator Charlie Cook a week ago. "These are districts that may have sent large numbers of their sons and daughters into Iraq, take a dimmer view of immigration, don't believe in deficits and are most disheartened by scandals."

But to win such seats, Democrats needed candidates who took a more moderate posture, particularly on social values. How moderate? Some 27 of the 40 most competitive Democratic House candidates pledged, if elected, to join the centrist New Democratic Caucus - a group that is anathema to the party's liberals.

A look at Democrats who picked off Republicans shows how different they are. They include pro-gun, pro-lifers (former minister Ted Strickland, Ohio governor-elect; ex-DA Bill Ritter, Colorado governor-elect); social moderates (Pennsylvania Sen.-elect Bob Casey Jr.; ex-NFL quarterback Heath Shuler in a North Carolina House seat) and ex-soldiers (Adm. Joe Sestak for a Pennsylvania House seat; Reagan Navy Secretary James Webb for the Senate from Virginia).

Tracking polls in the 50 top swing seats during the final weeks showed that, despite the widespread discontent over Iraq and scandal, there was no upsurge in liberalism before Election Day. Gay marriage, gun control and terrorism still worried voters. If the Democrats hadn't presented middle-of-the-road alternatives, Republican efforts to woo back voters on these issues might've worked.

In the end, the exit polls showed, Democratic House candidates took three in five moderate and independent voters. They also got half the suburban vote, and even took almost as large a share (48 percent) of rural voters, who Republicans seemed to have locked up earlier in this decade.

The location of the winners is just as telling. Half the Democratic House pickups were in the heartland. Had Democratic gains been limited to the coasts, there might well be no Democratic House majority today.

Ironically, this result validates Democratic National Chairman Howard Dean's "50-state strategy" - but with a corollary his left-wing backers would hate. It shows that Democrats can carry red states, but only if they reach out to independents and moderates.

The bloggers and activists can raise money and preach to the choir, but they are useless for converting the persuadable, hesitant voters in the middle. (Their ability to defeat Sen. Joe Lieberman in the Connecticut Democratic primary, but not the general election, underlined this.)

Indeed, it's clear that the notion dear to both the left-wing bloggers and conservative Bush strategist Karl Rove - that swing voters are few and elections won by revving up the base - is finished. The final-month swing-seat tracking polls had the share of persuadable voters fluctuating at 22 percent to 29 percent of the electorate.

The temptations of investigations, Iraq posturing and tax hikes will remain strong for many traditional Democrats in the next Congress. While this will be the largest Democratic caucus since 1994, it will also be the most moderate since then - because the party's growth occurred in its centrist wing.

The lesson for 2008 is that the party that wins the center is likely to take the White House as well as Congress. This year Democrats took a big step towards that goal, but they will reach it only if those who want their party to swerve left are kept at bay.