Kittery, Maine ? By 11 a.m. Chellie Pingree is working the second shift in a campaign day that started long before dawn at the gate to the Bath Iron Works.

The 47-year-old Democrat running against Susan Collins for the U.S. Senate is heading down the Maine Turnpike, speed-talking and dressed in a light-blue turtleneck sweater. This is the shade of blue that strategist Karl Rove chose when he color-coded Maine as a Senate seat the Republicans might lose. Pingree is running hard to keep that code blue.

To give you an idea of this woman’s tenacity, 30 years ago, Pingree came to North Haven, an island 12 miles off the coast of Maine with a year-round population of 350 people. Islanders then were, to put it mildly, wary about this young woman from “away.”

When she tried to volunteer at school, someone bumped down the dirt road to her house to deliver the message: “Tell that girl in the red pickup not to come near the schoolhouse.”

Pingree retells the story of her neighbors with a smile. “Twenty years later,” she says, “I was head of the school board.”

On the island, Pingree became a farmer, raised sheep and started a business that sold knitting kits. Then about a decade ago, in one year, she got divorced, sold her business, lost her father, and ran for office … with three teenage children. “And people wonder if I’m tough enough for this job,” she laughs.

As the majority leader of the Maine Senate, she got a corporate accountability bill passed in the days before you could even say those words out loud. She became the founding mother and force behind Maine Rx, a model plan allowing the state to negotiate with companies for lower cost prescription drugs.

When she proposed Maine Rx now facing a U.S. Supreme Court test a drug lobbyist warned her, “if you persist, I’ll never give you another campaign contribution.” She adds, dryly, “I gotta say, they’ve been true to their word.”

All this put Pingree in the light-blue spotlight when she decided to run against Collins. But her status as an underdog tells you something about Maine, about moderates, and about the success of a Republican strategy that political doctors call “inoculation.”

Collins is a member of that endangered species, a moderate Republican. It’s rarer in Washington than in Maine. Here the governor is an independent, both senators are Republican women, both congressmen are Democrats.

Pingree respects that independence in Maine voters “we’re straightforward, no-nonsense people” but wants to redefine the label “moderate.” “You don’t get to call yourself a moderate if you voted against the minimum wage. You don’t get to call yourself a moderate if you voted for the biggest tax cut for the rich.”

Indeed Collins has been late or “lite” on many of the issues that Pingree “owns.” But the senator has also been protected from easy attack. It is much harder for the voters to make distinctions and harder for an underdog to find a “wedge” when both parties have a prescription drug plan and when even the CEOs in the Bush inner circle promote some kind of corporate accountability.

But even if Collins is not Trent Lott, Pingree points out, “her first vote will be for Trent Lott.”

This has been the toughest case to make in too-close-to-call races from Maine to Missouri. With a Republican Senate added to a Republican White House and a Republican House of Representatives, one party controls the agenda. Back comes the estate tax repeal, the energy bill, the permanent tax cut. Up comes the next wave of judicial nominees.

Even a pro-choice Republican like Collins, who disagrees with the president more than most in their party, becomes effectively less moderate. That’s why Bush raised money for Collins, describing her as “kind of an independent thinker.” But “she’s an ally, and I’m proud to call her ‘friend.'”

The conventional wisdom says that voters don’t pick parties as much as people and policies. In Kittery, Pingree talks about jobs and health insurance. In a day or two, she’ll be on a bus taking senior citizens to Canada where they can get prescriptions filled for a fraction of what it costs in the States.

Meanwhile, her three children are heading a field team that’s knocked on 150,000 doors so far by their own count. And soon, she and Collins will face off in a series of debates where this natural campaigner should shine.

This is a place where political scientists like to say, “the center holds.” But this year, says Pingree, “Maine isn’t just making a choice for the state but for the nation.” Color that choice light blue.

Ellen Goodman is a columnist for Washington Post Writers Group.