President Barack Obama assailed critics of his health care initiative Saturday, seeking to grab the megaphone from his opponents and boost momentum in his drive for congressional passage of his chief domestic priority.

“I will not accept the status quo. Not this time. Not now,” the president told an estimated 15,000 people during a rally that had every feel of a campaign event, right down to chants of “Fired up, ready to go!” and “Yes, we can!”

Days after urging Democrats and Republicans in Congress to come together, an invigorated Obama said his plan incorporates ideas from those on both sides and he promised to continue to seek common ground.

“If you come to me with a serious set of proposals, I will be there to listen. My door is always open,” the president said.

But he warned that he wouldn’t waste time with people who have decided “that it’s better politics to kill this plan than improve it.” He also said he wouldn’t stand by while special interests “use the same old tactics to keep things exactly the way they are.” And he warned, “If you misrepresent what’s in the plan, we will call you out.”

The pitch came in friendly territory. Democratic-leaning Minnesota is one of the nation’s healthiest states, with relatively few uninsured residents, cost-effective medical care and top health care providers such as the Mayo Clinic.

His speech at the Target Center was part of a weekend campaign by the White House to give the president as much exposure as possible after his prime-time address Wednesday to Congress.

At the rally, on network television and in his weekend radio and Internet address, Obama again sought to take the reins of the debate, a task that has proved elusive over the past three months. The challenge is both to energize his supporters and make people with insurance care about his proposal.

In Minnesota, he cited a new Treasury Department analysis that found that nearly half of all people under age 65 go without health coverage at some point in a 10-year period. The data came from a study that tracked the insurance status of a sample of people from 1997-2006.

The report also found that 57 percent of those under 21 will find themselves without insurance at some point during a span of 10 years and that more than one-third of Americans will be without coverage for short periods that add up to a year or more over 10 years.

“In other words, it can happen to anyone,” Obama told the raucous Minneapolis crowd. “There but for the grace of God go I.”

The speech largely tracked the one days earlier on Capitol Hill, and he tore into opponents who he claimed were spreading rumors designed to scare people as they try to “bring Obama down.”

The president said he wants to see a government-run option in the plan and remains open on “how to set this up.” He stressed it would be one of many choices for people seeking affordable care and no one would be forced to opt for it.

In a CBS’ “60 Minutes” interview to air Sunday night, Obama said he’s focused on overhauling health care the right way. “I have no interest in having a bill get passed that fails. That doesn’t work,” he said.

He added: “I intend to be president for a while and once this bill passes, I own it.” And if it doesn’t work, Obama said: “I’m the one who’s going to be held responsible. So I have every incentive to get this right.”

While the president cleared out of town, thousands of people marched along Pennsylvania Avenue to the Capitol to protest Obama’s approach on health care and what they say is out-of-control federal spending. At the protest, people chanted “enough, enough” and “We the people” and carried signs that said “Obamacare makes me sick” and “I’m Not Your ATM.”

Reacting to the president’s new campaign, Senate Republican Leader Mitch McConnell of Kentucky said: “The status quo is unacceptable. But so are the alternatives that the administration and Democrats in Congress have proposed.”

In the weekly Republican address, Sen. John Cornyn of Texas said Obama has paid lip service to bipartisanship, rejected ideas that would bring the parties together around overhauling the system and ignored the American people’s wishes. He criticized the cost of Democrats’ health proposals and their long-term effect on the budget deficit, saying one of the House bills works out to $2.4 trillion over 10 years, beginning in 2013.

Obama puts the cost of his plan at $900 billion for the period starting in 2010, when more revenue will be available right away.

Said Cornyn: “President Obama should work with Republicans on a bottom-up solution that the American people can support.”