His campaign estimates 17,000 people showed up to the Comfort Dental Amphitheatre, which has a maximum capacity of more than 18,000.
Romney's delivery was matter-of-fact as he carefully gave his message with the use of a teleprompter.
The speech was his closing argument, some of which involved attacking President Obama.
"If the President is elected he'll still be unable to work with the people in Congress," Romney said. "He's ignored them, blamed them, attacked them."
Romney also accused the President of avoiding talking to Republican leaders in Congress about serious issues like jobs and the economy.
By way of his economic argument, Romney also made an interesting campaign promise.
"When I'm elected the economy in American jobs will still be stagnant of course, but I won't waste any time complaining about my predecessor," Romney said.
Romney also brought on stage a scoutmaster from Monument, Colorado. The scoutmaster was holding a flag his boys scout troop had on the Challenger space shuttle when it broke apart and crashed. The flag was recovered intact.
It's a story Romney has fondly pointed to in previous speeches on the campaign trail in Colorado.
Before the speech, the crowd was treated to an energetic musical performance by Randy Owen, the lead singer of the band Alabama.
The event was designed to evoke memories of last month's rally with Romney and Ryan at Red Rocks Amphitheater, which provided some of the best visual displays of support for Romney so far in the campaign.
(KUSA-TV © 2012 Multimedia Holdings Corporation)