Over the past 200 years, Brasil has experienced significant shocks to its political system. As the country turned the century into the year 1800 it was still a colony of Portugal, which held power across the Atlantic in Lisbon. But before the decade was over, the King of Portugal --João VI--was forced to move his family and throne to Brasil to escape the advances of Napoleon's forces across Europe. It's worth noting that this transmigration by a king from Europe to a colony in the New World was historic. Never before and never again would a king move the seat of power away from European shores. The year was 1808 and Portugal was permanently weakened.
By 1822, Brasil had declared its independence from the Portuguese crown. The newly designated emperor was Dom Pedro I, son of João VI. The father did not support the son however and João VI refused to recognize Dom Pedro's (and Brasil's) independence until 1825. Regardless of the family squabble, most historians refer to this time in Brasilian history as the Era of Empire: 1822-1888.
Eighteen eighty nine represents a turning point for Brasil. First, slavery was abolished. Second, it marks the end of Empire and the beginning of Republic. In many ways the new government fashioned itself after the United States, beginning with the its formal name as "The United States of Brazil." Although there was a dark side to its beginnings -- mainly in the power and influence of the military -- as a republic it sought to live up to the ideas embedded in the term res publica, which is Latin for "community." Eventually people received the right to vote and there was a separation of church and state. Historians refer to this era as The First Republic: 1889-1930.
Yet 1930 represents another important transition in Brasilian politics. Like many other countries, Brasil was impacted by the global economic collapse brought on by the 1929 crash on Wall Street. In Brasil this was known as the "Crisis." Perhaps even more importantly however was the military coup d'état which installed Getúlio Vargas as dictator for the next 15 years, an era known as Estado Novo (New State): 1930-1945.
The next segment of the Brasilian political roller coaster spans the complicated years from 1946-1964, when elections were reinstated and many freedoms, including freedom of the press, returned to the populace. Ironically, Vargas was elected president during these years but was hounded by that same free press and ended up committing suicide in 1954.
Freedom was short-lived however and another right wing coup d'état, accompanied by a new dictator -- Marshal Humberto Castelo Branco -- came to power in 1964. This dictatorship lasted from 1964-1985.
Since 1986 Brasil has once again enjoyed democracy. Currently Luiz Inácio Lula da Silva (usually referred to as Lula) is president, after having been elected for a second term in 2006. Lula is fairly popular, hence his re-election, and comes from a modest family. His background is comprised of union organizing, and he was a founding member of the party who eventually overturned the last military dictatorship.
Much of this information, except the most recent material, can be found in Robert M. Levine's The History of Brazil. New York: Palgrave MacMillan, 1999.