It's one thing for Hillary Clinton to attack Barack Obama, the overwhelmingly likely Democratic nominee, in terms virtually identical to those used by John McCain, his presumed general-election opponent. It's another thing for her to do this while explicitly praising McCain relative to Obama:
Defending her provocative television ad suggesting he was not up to the challenge of answering the White House phone at 3 a.m. in a crisis, she told reporters at a news conference Monday in Toledo: "I have a lifetime of experience I will bring to the White House. I know Senator McCain has a lifetime of experience he will bring to the White House. And Senator Obama has a speech he made in 2002" — a reference to the address in which Obama, before being elected to the Senate, had publicly opposed the Iraq invasion that she and McCain had voted to authorize.
There are certain lines that you do not cross in a primary campaign. And one of those is suggesting that your primary opponent, the likely nominee, is so unfit that that the Republican nominee might be preferable to him. This is spoiler territory, and Clinton should be ashamed.