Romney began his 30-minute address by praising Colorado's teen Olympic swimming champion, Missy Franklin, and honoring the victims of the Aurora theater shooting and their families.

"How about Missy Franklin. Isn't that something, huh? Isn't that something. Wow," he said.

"That is really exciting. Just a Colorado girl with a big heart."

"I met another Colorado girl with a big heart this morning. Her name is Micayla Hicks," Romney said, referring to a theater rampage survivor who is recovering after being shot in the mouth.

"I guess maybe by applause we show how united we are with the tragedy of those people, how much we love them, how much we care for them," Romney said, as the crowd rose in a standing ovation.

"Across the country, people are thinking about Aurora, and the tragedy there and the lives that have been lost and lives changed forever. We love you and we pray for you. You're in our hearts and you're in our prayers."

Launching into his speech, Romney said, "Today I come to talk about making things better."

The former Massachusetts governor ticked off ways he would strengthen the American economy, including promoting U.S. energy exploration, improving education, fighting for fair trade, cutting the national deficit and supporting the growth of job-creating small businesses.

Romney's biggest cheers came when he vowed to help businesses by striking down President Barack Obama's signature health care reform law.

"We've got to get rid of Obamacare," Romney said to loud applause.

He said he would defend the United States from unfair trade practices by countries like China.

"It's good for a nation like ours to trade with other nations. But if nations like China cheat, we got to stop that," Romney said to cheers.

"We can't let China walk all over us."

As for cutting the deficit, Romney said, "The way I will do this is by getting more growth and by also reducing spending."

"And our friends across the aisle and the president, they have a different view. They think, 'Well we should just raise taxes.'"

"The problem is this: Taxes are connected to growth. And when you raise taxes, you lower growth," he said.

Romney also gave Obama failing grades for not delivering on several 2008 campaign promises, including providing Americans with more home ownership and producing more higher-paying jobs.

As Massachusetts governor, Romney said he did create jobs and reduced unemployment.

He wrapped up by saying, "I can't wait to get to Washington!"

About a dozen gun control advocates protested outside the Romney rally.

They included members of Colorado Ceasefire and Mayors Against Illegal Guns.

Mayors Against Illegal Guns is led by New York City mayor Michael Bloomberg and Boston mayor Thomas Menino. The group is pushing for both Romney and Obama to come up with a plan to address gun violence.

Colorado Ceasefire is led by Tom Mauser, whose son was killed in the 1999 Columbine shootings.

After the speech, Romney traveled to Basalt for a Republican Governor's Association meeting.

There, Romney said he's looking forward to working with GOP governors like Chris Christie of New Jersey, Nikki Haley of South Carolina and Virginia's Bob McDonnell.

Those governors and others joined Romney at a rally Thursday in Aspen, where the Republican Governors Association is meeting.

Other attendees included Govs. Bobby Jindal of Louisiana and Susana Martinez of New Mexico.

Romney is expected to announce his running mate any day.

Haley said she'll fight to get Romney elected. Christie says Romney's a better leader than President Barack Obama. And McDonnell says Romney is focused on the middle class.

Romney visited Colorado last month. He stopped at a food bank in Colorado Springs that was working to help victims of the region's wildfires and he held several private fundraisers and receptions in Aspen.

In May, Romney made a campaign stop in Craig. Romney spoke at Alice Pleasant Park, then shook the hands of supporters in the large crowd.

Obama will campaign in Colorado on Aug. 8 and 9, Obama for America announced Wednesday.

Many experts say Colorado has become an important swing state that could decide who wins the White House in November.