Colorado remains critical for Barack Obama, and the candidate's campaign chief painted a scenario Thursday that showed the state being the tipping point foran Electoral College victory.

As campaign manager David Plouffe calculates it, Obama could be at 264 electoral votes on Election Day -- and the addition of Colorado's nine votes would send him over the top.

"Colorado is really ground zero for the presidential campaign," Plouffe said in a conference call. "The three Western states -- Nevada, Colorado and I'd add Montana to that -- are all going to be critical, but Colorado could be a tipping point.

"If we're able to hold on to all of John Kerry's states, which would give us 252 electoral votes, win a couple leaning our way right now -- Iowa and New Mexico -- that would put us on 264, and we'd be right on the doorstep."

The focuson Colorado was evident this week when Obama made stops in Grand Junction, Pueblo and Golden, and Republican vice presidential nominee Sarah Palin appeared Monday in Golden.

With polls tightening in Colorado -- the latest shows Republican John McCain up by 2 points -- the campaigns have been active throughout the state.

Plouffe said the Obama campaign is in better shape than Kerry in 2004, when Colorado ceased to be a battleground state in the waning days of the election and President Bush won the state by about 5 points.

An ambitious ground game -- including almost 30 campaign offices in the state -- is part of the Obama strategy, and Plouffe said they plan to be active in getting people to vote early once it starts Oct. 20.

McCain's campaign is also actively registering voters and believes it got a boost in Colorado with Palin on the ticket. McCain's frequent visits to Colorado show he's serious about winning here, the campaign says.