Every four years before an election, each political party holds a national convention. The convention is a meeting of party members called delegates. Delegates are loyal supporters of a political party. The attend the convention in support of a candidate and in support of the ideas that their party wants to promote.
The Republicans are holding their convention in Tampa, Florida this year. This will finalize the selection of Mitt Romney as their candidate for U.S. President. He will also be considered the leader of the entire Republican Party; however, there are other individuals and groups that maintain a lot of influence over Republican politicis.
The Democrats are holding their convention in Charlotte, North Carolina. There, President Obama and other Democrats will talk about what they have accomplished in the last four years and what they hope to accomplish in the upcoming four years.