After more than two decades in Frankfort, state Sen. Tim Shaughnessy, D-Louisville, announced Thursday that he will not seek re-election to the Kentucky Senate in 2012.Shaughnessy did not indicate why he was retiring, but thanked constituents for allowing him to be a public servant since 1988."I am grateful to the voters of my community for the honor and privilege of serving in the state Senate," he said in a statement.Shaughnessy says he will play an active role in the upcoming General Assembly in January, championing efforts to improve college graduation rates and heighten accountability within state Medicaid managed-care programs.Last year, Shaughnessy called for the shakeup of the Passport Health Plan board after a state audit found lavish spending.He also pushed for the commonwealth to use eminent domain after a homeless shelter purchased a hotel in downtown Louisville that lawmakers wanted to use for Jefferson Community and Technical College.