Many more were not able to get seats in Red Rocks Amphitheater to see Romney appear with his running mate Paul Ryan.
The entire event seemed to be built specifically to project an image of confidence and control for the Romney campaign.
That theme came through in Romney's speech. Early on, he belittled President Barack Obama's campaign.
"Look at the Obama campaign, it's reduced to talking about smaller and smaller things," Romney said. "They're talking about saving characters on Sesame Street. They're talking about silly word games. Day in and day out there is one attack after the other. Attacks on us, that does not make an agenda for the future."
The visuals were designed to compliment this image of confidence.
The crowd towered up from the stage, and supporters in colored shirts formed the shape of a Colorado flag as Romney logos in blue light splashed on to the red rocks towering to the sides of the crowds.
The stage itself was adorned with flags and banners reading "real recovery."
The crowd was treated to musical performances by Kid Rock and Rodney Atkins before the speeches, who played acoustic sets on a stage set with grass, that almost felt like sitting around a campfire.
Coupled with the projection of confidence was an urgent plea to supporters to help Romney turn out voters.
A strong ground game was largely credited with helping President Obama win Colorado in 2008.
Republicans are trying to match it.
"It matters for your kids, for 23 million Americans looking for jobs. It matters for the world. Colorado you can make it happen," Romney said.
President Obama's campaign felt that Romney was overconfident.
"The Mitt Romney we saw tonight in Colorado was dour, defensive, and dishonest-and it's no surprise why. Last night, he was exposed as reckless and wrong on foreign policy and failed to present any specific plans for what he'd do as President, " Obama campaign spokeswoman Lis Smith said.
Mr. Obama, who has drawn big crowds to his Colorado events, also plans a campaign rally this week in the Denver area.
He'll speak in City Park Wednesday as part of a three-state swing on the campaign trail.
One thing is clear: both campaigns still think they have a shot in Colorado in the final two weeks of the campaign.