WASHINGTON (CNN) -- President Obama's speech to Congress Wednesday on health care reform will probably be one of the high-noon moments of his presidency.

President Obama has faced pushback from members of his party on a public health care option.

Surrounded by liberals demanding a government-run public option and centrist Democrats -- along with Republicans -- who want to dump the option, Obama just might have his finger on something that can get him through this health care showdown: the "trigger" option.

The idea would give insurance companies a defined period to make changes in order to help cover more people and drive down long-term costs. If those changes failed to occur within the defined period, a trigger would provide for a public option to force change on the insurance companies.

A public option is a government-funded, government-run health care option, similar to Medicare. Under the plan, people would pay premiums 10 to 20 percent less than private insurance.

But the question remains about whether Obama will side with liberals in making a strong play for the public option. Though he has voiced his support, he has signaled over the past months that it's not the only option that could work.

"I continue to believe that a public option within that basket of insurance choices would help improve quality and bring down costs," Obama said Monday.

One of the bipartisan "Gang of Six" on the Senate Finance Committee, Sen. Olympia Snowe, R-Maine, has been actively negotiating with the White House.

The six met Tuesday to consider a plan by Senate Finance Committee Chairman Max Baucus, D-Montana, to drop the public option and tax the priciest insurance plans. The plan would also take a look at using health care co-ops.

"If [co-ops are] going to end up just the way we've known co-ops for 150 years in America, the answer is 'yes,' because they're consumer-driven, and all the consumers benefit from it," Sen. Chuck Grassley, a Republican on the Finance Committee, said on CNN's "American Morning" on Tuesday. "They're organized by members. There's no federal government running the co-ops."

Snowe has been pushing the idea of a safety net, or "trigger," for a public health care option as part of a key compromise. A source familiar with her negotiations with Obama said that's one of the things they're talking about.