Political parties play several important roles in a democracy. They organize candidates to run for office and help mobilize voters through fundraising, campaigning and get-out-the-vote efforts. Parties also help structure government by determining who leads legislative committees and by providing an opposition party to check the majority. In the US, the two-party system has endured since the early 1800s, though the parties themselves have realigned around new issues approximately every 30-32 years, such as the Civil War and New Deal eras. Today, parties function as institutions that organize national conventions and platforms, operate at state and local levels, and play influential roles in all branches of government.