Bhutto had been excluded from the country by Gen. Pervez Musharraf, who threatened to have her arrested and tried on corruption charges if she returned. (Her husband, Asif Zardari, faced even more serious such charges, having been known while first husband as "Mr. 10%" because of the cut he took on foreign contracts.)
Musharraf, however, has now been much weakened. His failure to deal effectively with militants in the northern areas, his invasion of the Red Mosque and seminary, and the recent slap in his face when the Supreme Court reinstated chief justice Iftikhar Chaudhry-- all these events have left him reeling. As a military dictator, Musharraf lacks grass roots.
Under attack from the Muslim religious Right, he may seek the support of the secular, left of center Pakistan People's Party and allow Ms. Bhutto to return. She has now said she is coming back, even without such a deal. She says that her return is necessary to forestall a take-over of Pakistan by Muslim extremists sometime during the next 5 years. See the video below: