Denver has the largest number, 390k. Jefferson County (Golden, Coors country) now has more than El Paso (Colorado Springs.) Jeffco has 352k to El Paso's 347k. The counties with the most registered voters after the top three are: Arapahoe (very suburban) with 319k, Boulder and Adams with 205k each, followed by Larimer (Northern Colorado) with 200k, and Douglas (just north of Colorado Springs and equally as conservative)with 172k.

Here's where it gets tricky: There are huge numbers of unaffiliated voters.

• Dems 955k
• Republicans 1029k
• Unaffiliated 1022k

In the largest counties, the numbers are:

• Denver 182k Dem, 71k Rep., 135k Unaffil.
• El Paso 75kD, 158kR, 113kU
• Jefferson 110kD, 124kR, 117kU,
• Arapaahoe: 105kD, 110kR, 103U
• Boulder 83kD, 42kR, 78kU

• Adams 73kD, 55kR, 76kU
• Larimer 55kD, 72kR,71kU
• Douglas 36kD, 84R, 52kU

In addition to reaching out to unaffiliated voters, Team Obama is making a huge push to register new voters and get out the vote.

Take Aspen, in Pitkin County, which has almost 13,000 voters, 5,600 of whom are unaffiliated. 4,200 are Dems and 2,600 are Republicans. The Aspen Daily News reports today:

The overwhelmingly Democratic-voting Pitkin County — where Democratic candidate John Kerry received more than twice as many votes as President George W. Bush in 2004 — is being targeted as a voting sector that can put Obama over the top for Colorado’s nine electoral votes. Because any vote from this area is most likely a vote for Obama, his local boosters are focused primarily on registering as many locals as they can.

“One of the fallacies about Pitkin County is that people don’t need to go vote for a Democrat because everybody is voting for them anyway,” said Blanca O’Leary, co-chair of the county’s Democratic party. “What we need to do is make sure Pitkin County over-performs.”

The strategy worked in a local race in 2006:

Aspen Mayor Mick Ireland, an Obama supporter, cited the 2006 election of state Sen. Gail Schwartz as proof that this supercharged Pitkin County strategy works. In that contest, Schwartz pulled 82 percent of the Pitkin County vote after a similar local voter registration push. Ireland said the Pitkin County vote overrode more conservative sections of the district and propelled Schwartz’s narrow victory over Republican incumbent Lewis Entz. “We totally outweighed Delta County,” Ireland said.

As to the effort being expended:

These local Obama volunteers have been hitting the streets twice every week, on Saturday mornings and Wednesday afternoons, usually with a team of eight to a dozen. A smaller squad in Basalt does the same.

This weekend, Colorado Obama volunteers were matched up in a contest with those in Virginia in which the canvasser from those two states who knocks on the most doors gets to meet the candidate himself.

Nor is Obama overlooking the redder portions of the Western Slope:

Last week also saw Obama’s top adviser on veterans’ issues holding a forum in Grand Junction, Sen. Ken Salazar telling Colorado reporters in a conference call that Obama “as president will stand up for rural Colorado,” and New Mexico Gov. Bill Richardson touring Colorado addressing concerns of Latino voters and registering people to vote.

Obama is also pushing early voting which begins October 20 in Colorado.

[L]ocal Obama supporters are taking over Paepcke Park on Oct. 19 to push a less traditional campaign strategy: encouraging early voting..... They are worried that this year’s extra-long ballot in Pitkin County will cause extra-long lines at voting booths that might turn some people away on Election Day. Between local, state and national items, the ballot here is expected to have more than 30 questions and contests for voters to decide.

Obama has 32 campaign offices in Colorado. Nationally, he has 330 offices to McCain's 100.

Obama’s 50-state web of local offices is fueled by what is believed to be the largest field operation in American political history. And even veteran politicos are taken aback by the magnitude of his standing volunteer army.

“This is the best organized campaign I’ve seen,” said [Blanca]O’Leary, the county Democratic co-chair. “And I’ve been doing this forever.”

So, can Obama's get out the vote effort generate enough new voters to cancel out the smaller, largely Republican counties? And is there any way to predict which way the unaffiliated voters in the big counties will go?