1. The tireless, and occasionally tiresome, advocacy on behalf of liberal bloggers and interest groups for the public option. Whatever you think of their tactics -- I haven't always agreed with them -- the sheer amount of focus and energy expended on their behalf has been very important, keeping the issue alive in the public debate.
2. The fact that the CBO thinks it will save money.
3. The seeming inevitability of health care reform, which neuters the voices of those who aren't opposed to the public option per se so much as the entire project of health care reform.
4. The fact that the locus of power has shifted from the Gang of Six -- Bingaman/Conrad/Baucus/Snowe/Grassley/Enzi to the Group of Six -- Pelosi/Dodd/Obama/Reid/Baucus/Snowe.
5. The "innovation" of the opt-in/opt-out family of compromises, which have more liberal "street cred" than co-ops or triggers and are potentially also much more politically advantageous.
6. The fading from memory of the tea party protests and the "government takeover" meme.
7. Polls in myriad swing states and swing districts showing the public option is reasonably popular in these regions.
8. Constituent letters and e-mails.
9. The insurance industry's "senior moment": forgetting that this isn't 1993 and that the shelf life of a misleading study would be measured in hours (rather than days or weeks) and would damage its credibility in the process.
10. The Washington Post's somewhat bizarre decision to make its poll showing support for the public option its lede in yesterday's paper, even though public opinion has been fairly steady on the issue for months.