The incumbent carried a strong lead over Ron Fisher for the nomination by a vote of 3,551 to 2,370.
Fisher, who lost his first race for Buchanan County Sheriff in 2008 by 366 votes, sat with friends and family at his home while watching Strong's lead slip further and further away.
At one point, a family member said Strong was up by 500 votes. Fisher knew it was a deep hole to climb out of in the race for sheriff.
"Like I've been saying, it has been a tough race," said Fisher. "My family has been great, my wife and daughter, a lot of friends helping me a whole bunch."
Strong will face Republican Pat Grove on the November ballot.
Strong is seeking his third term as Buchanan County Sheriff.