WHY THE SENATE BILL MAY INCLUDE A PUBLIC OPTION: The public option was front and center again yesterday, with President Obama's senior aides reiterating the White House position that Obama supports a government-run option -- but isn't demanding one. Fortunately for public-option supporters, they may not need much more presidential support now that reform has fallen into Senate Majority Leader Reid's lap. Unions and progressives have been aggressively railing against a Senate Finance bill that they call a giveaway to insurance companies. And this week, progressives will begin running ads in Reid's home state of Nevada asking whether he's strong enough to get a public option passed. The conventional wisdom has been that Reid would not include a public option in the bill he takes to the floor, but would give liberals the chance to add it later. Now, Reid could diffuse a lot of progressives' animus by doing the reverse - including a public option in the bill he brings to the floor, but giving opponents the chance to strip it out. The move could increase his progressive cred and prevent a backlash from the very allies whose help he will need in what's shaping up to be a very tough reelection campaign.