Fixing what ails the state requires Illinoisans of all political stripes to be honest about how they got here.

Mandating more reasonable spending growth is the first step in a journey back to solvency for Illinois. The cap provides certainty today for a more responsible state government tomorrow.

Even after a 32 percent income tax hike, the Illinois General Assembly passed a state budget in 2017 that will generate an estimated $1.5 billion deficit in fiscal year 2018. That deficit is projected to grow to $2.15 billion in fiscal year 2019, according to the Governor’s Office of Management and Budget, or GOMB. The...