Frogumvir

I am interested in finding out what primary sources are recommended on the subject of the senatorial order throughout the centuries of the Republic. Also, what do you think was the key to it becoming perhaps the most important element of the Roman government? It seems that the fact that it was comprised of magistrates and ex-magistrates, as well as the fact that Roman culture was hierarcichal and tradition based aided the senate massively. It senatus consultum were treated in a manner similar to laws.