In comments to Marc Ambinder, the McCain campaign has resoundingly confirmed what Nate and Sean had to say about Sarah Palin’s continuing importance to the ticket. She is critically important to the campaign’s efforts to mount any kind of ground game.

Here’s Sean, who has been road-tripping to gauge field operations of both campaigns.

As most of you know, I’ve been on the road for the past three weeks, so far visiting at least a dozen McCain campaign offices in six battleground states as well as Palin’s first solo rally in Carson City, Nevada. If McCain dumps Palin, it is over.

In the Colorado Springs volunteer office, “you could hear a pin drop” in the days before Palin was picked. In Reno, the volunteering had been anemic; the Saturday morning after the Palin pick, organizers arrived to an early morning volunteer line waiting at the door.

Our direct observation shows McCain is being overwhelmingly outworked on the ground as it is; take Palin away and you can add 2-5% to Obama’s total in every close state due to ground game.

And here’s the McCain campaign.

Palin is directly responsible for doubling the size of the campaign’s field operation, according to a senior campaign official, as she’s been a huge fundraising draw, bringing in, according one reliable estimate, more than $30 million for the RNC and its joint accounts. In the 12 hours after the announcement, she raised $4.4 million for the campaign.

She is directly responsible for luring more than 100,000 people to McCain-Palin events — and that’s on the low end of a guesstimate.

She has helped the campaign recruit thousands of additional volunteers. In the last two weeks, for the first time this year, the campaign has recorded more volunteer door knocks and phone calls than the same weeks 4 years ago.

 "Given that 2004 is the measuring stick, we’re proud of that," a campaign official says. "We were nowhere close to 2004 stats until about 3 weeks ago."

Her choice has gotten some of the louder social conservative voices to shut the heck up and stop complaining about McCain. The money and people that she has brought has been put towards opening at least 100 new field offices over the past two weeks alone.

Had McCain not found a way to gin up enthusiasm for his ticket, his get-out-the-vote machine would likely be half its size. [my emphasis]

Now, I’m not surprised in the least that two McCain officials are confirming what Sean has to say–Sean’s doing some of the most valuable reporting of the campaign this year, showing us data that doesn’t make the polls or the pundits. And empty campaign offices are a pretty sound measure of the ineffectiveness of a campaign’s ground game.

But I am shocked by the clarity of the confession these campaign officials made–all in an attempt to refute the appearance that Palin has become an anvil for the campaign. That is that, up until ten weeks before the election, the McCain campaign was far under-performing their field goals, perhaps by as much as half. 

Now, given the fact they out-performed the same-week totals from 2004 in the last two weeks, they’re obviously trying to play catch-up.  Probably, they’re trying to combine voter ID with persuasion, particularly in places like OH and GA that are already voting.

But in some key ways, you can’t make up for the two month advantage Obama has had. You can’t build the kind of block-by-block campaign organization you ideally want if you don’t start recruiting volunteers in earnest until mid-September. You can talk to voters, but you can’t really establish a relationship with them, nor amplify the efforts of each volunteer over time.

Nate and Sean are right. The McCain campaign will have to win or lose with Sarah Palin. But in their attempt to convince Ambinder that she remains critical to the ticket, these McCain staffers have admitted that McCain has already badly lost in a key measure of the campaign.