Shailagh Murray and Lori Montgomery report in the October 24th The Washington Post:

Democratic leaders in the Senate and House have concluded that a government-run insurance plan is the cheapest way to expand health coverage, and they sought Friday to rally support for the idea, prospects for which have gone in a few short weeks from bleak to bright.

Murray and Montgomery first note:

In an early estimate of the House bill, the Congressional Budget Office forecast that fewer than 12 million people would buy insurance through the government plan.

This is true, by itself, but then Murray and Montgomery later report:

Because a government-run plan would be dedicated to holding down costs and would lack a profit motive, congressional budget analysts predict that it could reduce the cost of expanding coverage to people who don’t have it by as much as $100 billion over the next decade.

This is also true, but now Murray and Montgomery are taking the most pro-public option news out the first CBO report (that it would only enroll 12 million Americans), and conflating it with a later CBO report the full details of which Speaker Pelosi never made public. This makes it seem like the CBO believes that the public plan would only enroll 12 million Americans and would save $100 billion a year. This is simply not true: the CBO never issued a report saying that.

As the Lewin Group has clearly laid out in a letter explaining why they estimated a public plan would enroll 103.4 million Americans compared to the CBO’s 12 million estimate, the level at which the government pays health care providers will significantly effect both the number of Americans on the public plan and the amount of money saved. The lower the reimbursements, the more Americans are forced onto the plan and the higher the savings. The higher the rates, the less people are forced out of their existing insurance and the lower the savings.

Murray and Montgomery completely obscure this trade off by using numbers from two completely different CBO reports.