In a hallway outside the auditorium at Denver’s North High School, Sen. Mark Udall opened his wallet and pulled out his insurance card.

He and his family are enrolled in the state’s version of the Affordable Care Act, Connect for Health Colorado. He said he made the decision to do so last year when his federal health care plan was expiring.

“Like many Coloradans, I found the transition a bit rocky, but by going through the process I understand it,” he said Saturday.

Udall was just minutes from addressing the Denver County Democratic Party assembly. He had already been to Jefferson and Douglas counties, where in rousing speeches he told delegates that with their help he will defeat Republican Congressman Cory Gardner in November.

It was Udall’s support for Obamacare, as it is called, that prompted Gardner to abandon a safe congressional seat and challenge Udall. Part of the national Republican strategy to take control of the U.S. Senate hinges on attacking Democrats on problems with the rollout of the new insurance program.

Gardner spoke at Republican assemblies in Weld, Adams, Arapahoe and El Paso counties, where he made sure Obamacare was part of his speech.

“Mark Udall cast the deciding vote on Obamacare, and, as a result, millions of people across the country lost their health care,” Gardner told Republicans.

In an interview with The Denver Post, Udall on Saturday was asked about a statement he made to 850 KOA

that implied he didn’t vote for the Affordable Care Act, when he did.

“I think, look, if I were there, I would say, ‘Here are some things that we should have done differently, here are some things that make more sense,’ ” he told KOA. Udall said he meant to say “If I were there again.” In hindsight, he said, he should have pushed back in 2010 for “better implementation and a clearer provision that you could keep your insurance policy if you like.”

He said insurance companies “did not keep faith” with that provision, and he both “drafted legislation and put pressure on the White House to provide that option for people here in Colorado.”

“They responded to that call,” Udall said. “You can now keep your plan going forward.”

Udall added that health care reform was needed because insurance companies were dropping clients who got sick and refusing to cover women’s health issues.

“Coloradans want to make it work,” he said. “They’re not interested in another round of debates about repealing it.”

At the Denver Democratic assembly, chairman Ed Hall’s introduction of Udall was brief but enough to get delegates cheering.

“He voted against the war in Iraq. He voted against the Patriot Act. He is working to rein in the NSA,” Hall said. “This guy is great.”

The cheers continued when Udall took the microphone.

• “I’m going to fight to protect a woman’s right to choose to my dying day.”

• “It’s past time to raise the federal minimum wage. If you work, you shouldn’t live in poverty.”

• “I think it’s time we pass the Paycheck Fairness Act so women are paid the same as men. Do you agree?”

Udall, who has scaled mountains all over the world, ended his speech talking about climbing and winning.

“You don’t schmooze your way up a mountain. You don’t climb a mountain by accident,” he said. “Let’s get it done.”

Lynn Bartels: 303-954-5327, lbartels@denverpost.com or twitter.com/lynn_bartels