A Prestonsburg bankruptcy attorney will be the state's top financial officer.
Unofficial results showed Republican Allison Ball with 61 percent of the vote to 39 percent for state Rep. Rick Nelson, a Democrat from Middlesboro.
Ball's margin of victory was much larger than recent polling had indicated. In a late October Bluegrass Poll, Ball had 37 percent of the vote with Nelson at 35 percent. In that poll, 25 percent of voters were undecided, showing that many had not yet paid attention to the race.
Ball, 34, told voters she would be an advocate for taxpayers and said the office should be a "check and balance on spending in order to protect the state's financial stability."
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Ball credited her victory to her financial background and her pledge to be a watchdog.
"I have fresh eyes to keep track of every dollar the state spends and I pledge to do that," she said at the Republicans' victory celebration in Louisville.
Nelson, 61, campaigned on his experience in the state legislature and his years as a retired teacher.
As state treasurer, Ball will sit on the board of the Kentucky Teachers Retirement System, the Kentucky Lottery Board, several other boards and will manage the state's checkbook.
Ball out-raised and outspent Nelson, according to campaign finance reports. Ball also ran advertisements on television in the week leading up to Tuesday's election.
The latest campaign financial reports filed with the Kentucky Registry of Election Finance on Oct. 19 showed Ball raising $120,069 compared to Nelson's $65,024.
In the final weeks of the campaign, Ball still had $88,427 on hand while Nelson showed only $19,516.
State Treasurer Todd Hollenbach, a Democrat from Louisville, could not seek re-election because of term limits. The position pays $117,329 a year.
Asked what she would doing Wednesday, Ball said, "Sleeping."