Hillary Clinton will do her best to walk back her rhetoric over the last six months when she officially endorses Barack Obama for the nomination and general election. Her reluctance to concede the race on Tuesday makes this even more awkward, and she will have to show some real enthusiasm for Obama. That will require a lot of work, especially given all of the blasts she has leveled against the nominee for the past four months:

After a tumultuous 17-month journey, Sen. Hillary Rodham Clinton (N.Y.) will formally withdraw as a presidential candidate today, publicly declaring her support for Sen. Barack Obama (Ill.) for the first time since he secured the Democratic nomination.

Clinton drew the wrath of many Democrats when she did not acknowledge Obama’s victory in her speech on Tuesday night. Her farewell address to supporters, scheduled for noon today at the National Building Museum at Fourth and F streets NW, is intended to repair any lingering damage from the Tuesday speech and will close the door on an epic primary campaign that, after dividing Democrats, produced the first African American presumptive nominee of any major party in history.

The two candidates wound up meeting on Thursday night at Dianne Feinstein’s house in DC, a useful and neutral setting for the beginning of their rapprochement. According to Senator Feinstein, she greeted them and then left them alone for an hour to talk between themselves with no staff present at all. At the end of the hour, they were in a jovial mood, so the ice had been broken at the very least. Feinstein says she has no idea what was discussed or what agreements were reached, but Clinton scheduled her concession for today shortly afterwards.

Can she win back her supporters to Obama’s side? Perhaps the better question will be whether she can retain any credibility while doing so. She has a lot of explaining to do as to why she thinks Obama has more qualifications to be commander-in-chief other than “a speech he gave in 2002”, and where he acquired those credentials in the few short months since she made that accusation. Hillary has to also explain how Obama stopped “dangerously oversimplifying” foreign policy in a time of war:

The problem for Hillary is that these statements stick because they have a great deal of truth in them. The RNC has a library of these comments ready for ads in the fall. Every time she hits the road for Obama, the Republicans will remind voters of Hillary’s real opinions of Barack Obama. She’ll either have to say she was lying then or come up with ridiculous rationales to pretend that Obama has overcome these gaping liabilities — and with Obama making gaffe after gaffe, those rationales will look very weak.