Why is Giuliani able to sit back and watch McCain and Romney pummel each other?

Strange, no?

It is an unusual dynamic, to have the candidates placing second and third in most national opinion polls engaging one another fiercely, while allowing the front-runner a wide berth. But campaign officials and outside political consultants said that McCain's willingness to directly engage Romney appeared to stem from a combination of tactical, political, and, to a lesser extent, personal considerations.
Tactically, McCain and Romney are in direct competition because they have both invested enormous resources to compete in the early nominating contests in Iowa, New Hampshire and South Carolina. Giuliani, though, seems to be leaning toward competing more heavily in the large states, including California and New York, holding their primaries on Feb. 5. Several state-by-state polls have shown Romney gaining ground — even holding leads, in some — in Iowa and New Hampshire.....

On top of that, Romney and McCain are competing for conservative support....

Add to that the personal factor. McCain and Giuliani have something of a political friendship. Giuliani bucked much of New York's Republican establishment in 2000 when it tried to keep McCain off the primary ballot. The two men have taken in a number of ballgames together, not to mention meals in Little Italy.