David Anderson (2003) reports the elections were judged free and fair by local and international observers, and seemed to mark a turning point in Kenya's democratic evolution. In 2005, Kenyans rejected a plan to replace the 1963 independence constitution with a new one. As a result, the elections of 2007 took place following the procedure set by the old constitution. Kibaki was re-elected in highly contested elections marred by political and ethnic violence. The main opposition leader, Raila Odinga, claimed that the election results were rigged and that he was the rightfully elected president. In the ensuing violence, 1,500 people were killed and another 600,000 were internally displaced, making it the worst post-election violence in Kenya. To stop the death and displacement of people, Kibaki and Odinga agreed to work together, with the latter taking the position of a prime minister. This made Odinga the second prime minister of Kenya. In July 2010, Kenya partnered with other East African countries to form the new East African Common Market within the East African Community. In August 2010, Kenyans held a referendum and passed a new constitution, which limited presidential powers and devolved the central government. Following the passage of the new constitution, Kenya became a presidential representative democratic republic, whereby the President of Kenya is both head of state and head of government, and of a multi-party system. The new constitution also states that executive powers are exercised by the executive branch of government, headed by the president, who chairs the cabinet that is composed of people chosen from outside parliament. Legislative power is vested exclusively in Parliament. The judiciary is independent of the executive and the legislature. Mwai Kibaki became the first president to serve under this new constitution while Uhuru Kenyatta became the first president elected under this constitution. In 2011, Kenya began sending troops to Somalia to fight the Islamic terror group Al-Shabaab. In mid-2011, two consecutive missed rainy seasons precipitated the worst drought in East Africa seen in 60 years. The northwestern Turkana region was especially affected, with local schools shut down as a result. The crisis was reportedly over by early 2012 because of coordinated relief efforts. Aid agencies subsequently shifted their emphasis to recovery initiatives, including digging irrigation canals and distributing plant seeds. In 2013, Kenya held its first general elections after the new constitution had been passed. Uhuru Kenyatta won in a disputed election result, leading to a petition by the opposition leader, Raila Odinga. The supreme court upheld the election results and President Kenyatta began his term with William Ruto as the deputy president.