DENVER -- Maria Piñon turned 18 one week before Election Day, and celebrated Tuesday with a vote for Sen. Barack Obama.
The orthodontic assistant, who came to the polling place in her working-class Hispanic neighborhood wearing scrubs, said her family and friends voted the same.
"He's something new, something fresh to bring to our country," the first-time voter said. "I feel like my vote's going to make a big difference."
Voters like Piñon are part of the reason this battleground state gave its nine electoral votes to Obama.
The Centennial State used to be reliably red in presidential races. The last time voters here anointed a Democrat was in 1992, when Colorado went to Bill Clinton, and that was an anomaly.
But population changes have fueled a political transformation. Registration in the state has grown by 700,000 in the last decade, surging to 3.2 million now.
Among the new voters are large numbers of Hispanics and transplants from other states, especially California.
"The thing about Colorado, like the other intermountain West states, it's not just people changing their mind about candidates. It's new people coming in," says William Frey, a demographer at the Brookings Institution.
For instance, there was an 18% increase in eligible Hispanic voters in Colorado between 2000 and 2006, according to a report Frey co-authored using Census data. Hispanic voters, he says, tend to vote Democratic.
Mi Familia Vota, a group that encourages civic participation among Hispanics and immigrants, says it registered 2,300 people since late May by visiting churches after Spanish-language Masses, staffing tables outside Mexican groceries and courting newly naturalized Americans at citizenship ceremonies.
Eighty percent of the voters they added are Hispanic, said Grace Lopez Ramirez, the group's state director. Some were new citizens, and some had been here for generations but felt alienated from the process, she said.
"We want to empower our community through voting," she said.
The state wasn't solidly for Obama. In heavily Republican Douglas County, a southern suburb of Denver, Chantel Seas, 24, of Parker, opted for McCain.
Seas, a cosmetologist who is a registered Republican, said she was undecided until Monday.
She pointed to her 9-month-old daughter, Faith, as the deciding factor. She said she believes McCain's policies would be better for her family than Obama's. "He's really trying to work for families," she said. "He does want to tax health benefits, but he wants to make them available to everybody."
Even in Douglas County, however, some previously red voters turned blue. Dave Crowe, 51, a registered Democrat, voted for George W. Bush in 2000 and 2004. Crowe, a maintenance supervisor for the local school district, is a hunter, and said he has reservations about Obama's positions on gun control. He also worries that Obama doesn't have enough foreign-policy experience.
It was Obama's position on the economy that won him over.
"It was a very difficult decision, but he has the best economic plan for the country now," Crowe said.
Democrat Mark Udall, a strong environmental advocate, defeated Republican Bob Schaffer, a former congressman aligned with his party's conservative wing, in their battle for Colorado's open Senate seat, one of only five nationwide.
The 58-year-old Udall succeeds two-term Republican Sen. Wayne Allard, who is retiring.
The ferocity of the fight was broadcast in hard-hitting TV and radio ads financed by combined campaign spending of more than $17 million.
"I confess to you, this is the toughest climb I've ever taken," Udall, an avid mountaineer, told supporters in Denver.
His win gave Colorado two Democratic senators for the first time since the mid-1970s, when Gary Hart and Floyd Haskell served together.
Udall has represented Colorado's 2nd Congressional District for 10 years. A member of one of the West's most prominent political families, Udall stressed his roots in a region where Democrats have had to play more to the center to get elected.
Schaffer, who represented eastern Colorado's 4th Congressional District from 1997 to 2003, lost a U.S. Senate primary in 2004 after GOP leaders worried that he was too conservative to win statewide. He insisted that his principles of small government and low taxes are centrist and that the country needed the kind of balance a senator like himself would provide.
The race between Udall, 58, and Schaffer, 46, was watched nationally because it provided Democrats another chance to build their majority in the Senate. Their debates were heated, with the more low-key Udall and the more hard-charging Schaffer struggling to talk over each other at times.
A televised faceoff on NBC's "Meet the Press" turned combative after Schaffer interrupted Udall during questions about the $700 billion bailout of the U.S. financial system.
Environmental and left-leaning groups weighed in with jabs at Schaffer as "Big Oil Bob" because of his votes while in Congress and his work for a Denver energy company.
Schaffer shot back with ads touting his support for renewable energy and accusing Udall of blocking domestic energy production by opposing drilling.
"He has been and is still against the ability of the U.S. to expand its energy," Schaffer said of Udall.
Udall has tempered his opposition to offshore oil drilling but maintained his go-slow approach to commercial oil shale development and backing for renewable energy.
• Colorado voters on Tuesday soundly defeated a measure that would have defined life as beginning at conception, which would have been the first of its kind in the nation.
The proposed amendment would have said a person was "any human being from the moment of fertilization." With 38% of the vote counted, the measure was losing 74-26%.
It was spearheaded by a 21-year-old student who said her only goal was to define when human life begins. Any additional discussion would have been up to lawmakers.
Opponents contended it could be used to outlaw abortion, fertility treatments which can require the disposal of fertilized eggs and some forms of contraception.
Voters across all age groups and majorities of both men and women opposed the measure, according to an Associated Press poll of voters over the past week. Republicans and white evangelical voters showed the most support for it.
Laura Koke, a 26-year-old unaffiliated voter from Denver said it was one of the issues that drew her to the polls so she could vote against it. "I'm pro-choice. I think it creates a slippery slope. I wouldn't want my reproductive rights taken from me," said Koke, a contract manager for a consulting firm.
It was one of 13 ballot questions that Colorado voters faced.
• Others included whether to bar affirmative action in state hiring and contracting and increasing taxes on oil and gas companies.
The affirmative action proposal was backed by Ward Connerly, a former University of California regent who has helped pass similar proposals in California, Michigan and Washington state. Connerly pointed to Barack Obama's candidacy as proof that preferences based on race or gender are no longer needed.
Colorado voters appeared to be evenly split on the affirmative action issue. With 78% of the projected vote counted, the measure was failing 51-49%.
• Voters also weighed in on three measures strongly opposed by unions, including a measure to turn Colorado into a true "right to work" state.
Amendment 47 would bar "closed shops" in unionized workplaces. No one can be forced to join a union but currently unions can force non-members to pay dues to represent them if 75% of workers agree.
• Voters also were asked to give up future surplus tax refunds to provide more money for schools; whether to allow mountain gambling towns to consider raising gaming stakes and keep casinos open all night and to lower the minimum age for serving in the legislature from 25 to 21.
• Referendum O would require backers of constitutional amendments to collect more signatures from across the state in order to get the issue on the ballot.
Contributing: Associated Press