Regime change

In book 8 of the republic, Plato considers regime change. Democracy has the tendency towards tyranny. Why?
This is a paper based on textual evidence from Platos "the republic". This is the Alan bloom version. I have included the essay guidelines. ONLY use book 1, 2, and 8 of the republic to find quotes and such. Thank you so much. This is the link to the version. http://www.inp.uw.edu.pl/mdsie/Political_Thought/Plato-Republic.pdf