What are the functions of political parties in democracies?

What are the functions of political parties in democracies?
Why are the different types of party systems?
How has political party influence changed over time?
Why is it important for political parties to get people elected?
What is the best way to advance in a political party?
Who votes and does not vote in elections?
What impact does electoral realignment have in politics?
What do you think the future of the Republican Party is?

Include at least one reference (book, journal article, etc.)

Make sure your answer is at least 2-3 pages long, typed, and double spaced.