Rupf made his announcement last week, with more than a year left in his current term in office. The 66-year-old has been with the Sheriff's Office for more than four decades, starting as a deputy and working his way up through the ranks.
The Sheriff's Office has come under heavy criticism in the past several weeks after it was learned that a deputy failed to follow up on a citizen report that could have led to the discovery of recovered kidnap victim Jaycee Dugard three years ago.
Rupf offered a public apology after the information came to light, but has said that the incident and its negative impact on the department are not the reasons that he will be stepping down.
"This early announcement should not be taken as evidence that I've lost interest, enthusiasm or that I will not participate in a very direct and active fashion in all of our business," he said.
He explained that making the announcement early will allow members of the Sheriff's Office to prepare for a change in leadership and to allow ample time for other members of the law enforcement community to express interest in taking over the reins of the department.
"It is, however, timely that I do this so that the organization - after all our business is our overriding concern - will have an opportunity to make those adjustments in anticipation of a change at the highest level of the organization," he stated.
Appointed in 1992, Rupf was re-elected in 1994 and has been in office ever since. His decision to step down will mean that an election will be held in June 2010. The candidate elected to the sheriff's post will take office in January 2011.
Rupf said he had been considering retiring for some time, but setting down and actually making the announcement was hard for the career lawman.
"The decision was much more difficult than I had ever imagined," he offered. "But it is time; 45 is not only a good caliber, but it's a good number in describing years of a career."