Lebanon, N.H. ? There is a frosty undertow to the winds right now. Earlier this afternoon, walking around the pond, I felt winter’s chill breath on the back of my neck.

Right now, at dusk, the temperature at the peak of Mount Washington is 18 degrees, and it won’t be long before snow drapes the evergreens here on the lower elevations. But what is also being transformed, even faster than the atmosphere, is the landscape. It is changing, day by day, girding for what will come on the wintry winds.

These days, as New Hampshire’s taste turns from cold apple cider to hot, it is clear that the atmosphere and the landscape of politics have been transformed, too.

No longer a Republican state

Only a few weeks ago, when summer still seemed visible in the rear-view mirror, this was a Republican state – not quite as conservative as it had been a generation ago, when Barry Goldwater felt comfortable enough in New Hampshire to put forward ideas on privatizing Social Security that go even further than President Bush’s, but Republican enough to have a certain party purity to it. The congressional delegation was 100 percent Republican, the state House was 100 percent Republican, and the state Senate was 100 percent Republican.

That’s gone. New Hampshire’s voters elected two Democratic House members for the first time since 1912, and at the same moment, for the first time since 1911, these same voters installed Democrats in both the state Senate and state House. States turn over their political complexions all the time and we hardly notice. When it happens in New Hampshire, we can’t afford not to notice.

Sobering thought, but true: The New Hampshire primary, the nation’s first, is only 14 months away. It is here, amid the pines and birches and the newly ascendant Democrats, that candidates will test their messages and then be tested themselves. And though you know that Iowa’s caucuses come first, and the caucuses in Nevada, a newcomer to early presidential politics, now come next, remember that New Hampshire’s primary has a special quality that makes it a model for the national contest in November 2008: Independents can vote here.

Independent vote is key

That’s important. The Democratic caucuses in Iowa are almost certainly going to be dominated by the left. (The United Auto Workers are an important force in the state, skewing the trade debate, and anti-war forces in Ames and Iowa City are going to draw the Democrats leftward.) The Republican caucuses in Iowa are almost certainly going to be dominated by the right, and almost certainly by religious conservatives, who since 1988 have mastered the rhythm of these peculiar Monday evening contests. (Sen. Rick Santorum may have won only about 40 percent of the vote in his re-election fight in Pennsylvania, but 40 percent in the Iowa caucuses is a very big number. He may be out of the Senate beginning in January, but he’s still a political giant.)

The message of the midterm congressional elections is that the middle counts, and New Hampshire is well-positioned to move the campaign back toward the center. The old formula for success was to run at the extremes in the primary and then inch back to the middle in the general election. New Hampshire’s new political alignment, where independents are kings (or at least king-makers) transforms this state’s primary. It puts the prize in the middle of the political spectrum, not at the extremes.

This has been the case before, of course. In a very different age, before the state’s southern towns, now suburbs of Boston, acquired a Nouvelle Hampshire feel to them, with tapas and baked brie, Sen. Goldwater of Arizona on the right of the Republican Party took on Gov. Nelson A. Rockefeller of New York on the left of the Republican Party in 1964, and the winner was Henry Cabot Lodge, then the American ambassador to South Vietnam. Nearly seven years ago, in 2000, Sen. John McCain of Arizona delivered a stunning upset to Gov. George W. Bush of Texas.

The McCain victory is a telling lesson for 2008. Most Republicans agree that Mr. Bush prevailed among Republicans in the 2000 GOP primary. But that wasn’t enough. Mr. McCain courted independents, and won the allegiance of enough of them to claim a victory of 19 percentage points. Talk about a thumping.

Extremes are mobilized

Now we begin a race where both extremes are inflamed, the right with resentment over what it believes is the Bush administration’s abandonment of small-government principles and fiscal responsibility (both bedrock values of New Hampshire, which still lacks either a state income tax or a sales tax), and the left with anti-war passion (the same force that produced the poor showing by President Lyndon B. Johnson, leading to his withdrawal from the Democratic race).

Everywhere else the seething conservatives and the soaring Democrats will be mobilizing their forces and paying little attention to those who don’t share their fervor, giving a sense of unreality to the proceedings that isn’t healthy for either party, as a slew of left-leaning Democratic nominees in the late 20th century can attest. Here in New Hampshire the campaign will be fought in the middle.

That, after all, is where the country is. One of the branches of government is controlled by the Republicans. One of the branches just fell into Democratic control. And New Hampshire, leaning slightly left for the first time in a century after leaning right for so long, suddenly is Middle America.