His main challenger, Mir-Hossein Mousavi, disputes the election results, and his supporters clash with police in Tehran. The vote outcome may have broad consequences for U.S. foreign policy. Mahmoud Ahmadinejad sailed to a second four-year presidential term with a huge margin of victory amid allegations of widespread fraud and a strident challenge of the Iranian vote results by his main challenger, and protesters scuffled with police in riot gear throughout Tehran in what many described as the most serious clashes in the capital since a student uprising 10 years ago.