Three distinct groups of people are responsible for the amazing power and endurance of the "Sen. Collins is a moderate" narrative. And while any discussion of them runs the risk of overgeneralizing, the narrative is potent enough that it's a risk worth taking.
First, there's the GOP noise machine. This includes Collins' senate and campaign staffs; her Republican allies in DC and Augusta; and Republican-friendly pundits, journalists, interest groups and organizations.
These people know full well that Collins has been there for President Bush whenever he's needed her and that she's a reliable Republican when it counts.
But because airing these facts would imperil their interests, supporters downplay the truth and advance the "moderate" narrative to protect Collins politically. (There are, of course, occasional bursts of candor.)
The second group is made up of under-informed progressives: Gore and Kerry-supporting Mainers and others who've been hearing the "moderate" narrative so long that they've come to believe it.
These people will tell you they "like" Susan Collins. Pressed further, they'll tout the junior senator's credentials as (nominally) pro-choice, pro-gay and pro-environmental protection.
But they don't know details, and often aren't interested in them. And because they hear so little in the Maine media that undercuts the established view of Collins, they have little reason to question their impressions--which makes them all the more powerful as narrative proponents.
The last group is the hardest to pin down, which may make it the most important to discuss. Call it the "centrist caucus." This group is made up of politicians, journalists, editorial boards, interest groups and Mainers with a stake--tangible or just intellectual--in the idea of transcending partisanship.
So we're talking about people like New York City Mayor Michael Bloomberg, a life-long liberal who had no path to power through the Democratic party and so styled himself as a centrist Republican.
We're talking about Human Rights Campaign, which justified its endorsement of the junior senator largely on the basis of a desire to endorse candidates from both parties.
And we're talking about national journalists and pundits who, in an electoral climate extraordinarily favorable to Democrats, are looking for ways to demonstrate their non-partisan credentials by singling out one or two Republicans for praise.
But we're also talking about people who may be your friends and neighbors--unaligned voters who profess to despise the partisan nature of politics.
These people are hungry for politicians who will reject party orthodoxy, but sometimes seem indifferent about the substance of the issues involved. They want a stop to all the bickering, but don't always see the point of taking the time to determine who's right and who's wrong.
These people are less interested in results than in tone. They're driven much less by issues than by posture.
Some of them don't know the truth about Collins' record. Others do, but are willing to overlook it: After all, members of the centrist caucus need someone to champion as an exemplar of their politics.
And with the nation polarized and Republicans in denial, Collins' willingness (occasionally) to at least make the right noises is enough to distinguish her from most of her GOP colleagues.
To Mayor Michael Bloomberg, to Human Rights Campaign, to the Maine press--that's enough to qualify her as a moderate in good standing.
The power of the moderate myth--and the degree to which it's entrenched in Sen. Collins' political narrative--points to the difficulty of Rep. Allen's task in this election.
He needs to first educate Mainers about Collins' record and issues positions and then make the argument against them.
It's not an insurmountable task. But the two-tiered nature of the effort certainly adds to the challenge.