The calculated decision that Bill Clinton will lead his wife’s attack on Barack Obama — here and now, and increasingly leading up to the February 5 Super Tuesday primaries — represents a shift in the fundamental Democratic campaign dynamic, which is unnerving influential Democrats, both in her camp and Obama’s.

They fear that the campaign for the Democratic presidential nomination has thus taken on an ugly aspect that is already spinning out of control, and could damage the party’s chances in November; strip the former President of his unique position as the Democrats’ most popular and influential figure; and — worst of all — focus attention not on electing Sen. Hillary Clinton as president, but rather, the less palatable question of the Clintons’ — plural — restoration to the White House.

The whole question of Hillary Clinton, Bill Clinton, and their difficult relationship to the truth is now front and center. Or, as one of the Clintons’ suppoters put it to me, “The circus is back. Many Democrats may love Bill Clinton — and they do — but not many relish the prospect of the circus back on center-stage” in American life.

However, the Clintons believe this course — with Bill Clinton leading a careful but unrelenting attack on Obama’s credibility and credentials — may be the only way to reduce the chances that Hillary Clinton could get grievously injured in the February 5 Super Tuesday primaries and lose the nomination to Obama.

– CNN Contributor Carl BernsteinEditor’s note: Carl Bernstein discusses his views with Anderson on tonight’s 360 at 10p ET.