I think the case can be made that Russell Pearce has had more influence on Arizona policy in the last five years than any other legislator. However, it's not just in Arizona; illegal immigration has become a national issue largely because of his efforts. Here's an interesting profile of Pearce in Reason online. (The headline of the article is negative, but I think Pearce himself would be pleased with the body of the article.)
He wants to end birthright citizenship, slash immigration quotas, and throw up more walls. He has proposed that officials at the state's Child Protective Services be required to root out undocumented children. The representative of a city named Mesa, Pearce co-authored an initiative to ban the use of Spanish in most official communications. Most of all, he thinks anyone who puts "profits above patriotism" ought to be kept from doing business in the state of Arizona. In the summer of 2007, Pearce finally got his wish.