State officials will have lot of explaining to do as the Legislature unpacks Gov. LePage’s biennial budget proposal. One of the first explanations should be why rebuilding a prison has jumped to the top of the state’s infrastructure to-do list.

According to Gov. LePage’s recently released proposed budget for 2013-2014, the state would borrow $100 million to replace most of the buildings that make up the current Maine Correctional Center in Windham. The new facility would double the capacity of the existing institution.

The current prison, a hodgepodge of buildings assembled over the last eight decades, is said to be inefficient and expensive to manage.

LePage’s proposal may prove to make a lot of sense, but he first should explain why this project is a go while other investments are considered too costly.

Up until last week, he said he would not spend $100 million in bonds that were approved by the voters and two-thirds majorities in the Legislature. Those funds could have been used last summer to put construction workers on the job, repairing roads, boosting downtown development and improving buildings in the state’s public universities.

LePage has said that he wouldn’t issue the bonds until the state’s economy improved. He would not be swayed by arguments that the projects were approved by voters and would create at least temporary jobs. Historically low interest rates and competitive bidding during an economic downturn also didn’t convince him that this is a good time to borrow.

Now suddenly he’s ready to release those bonds, borrow money to repay the hospital debt and, inexplicably, rebuild the prison in Windham. What changed?

At the same time, the LePage administration is looking to cut health care programs for the needy, shift tax burden to municipalities and force school districts to raise more money or cut programs. School buildings are dilapidated in every corner of the state, and many are overcrowded or inefficient to operate.

So, with no increase in the crime rate, why is this a good time to invest in a bigger and more efficient prison system?

The case may be made, but it would be made more effectively if it followed an attempt to reduce prison costs by means short of new construction.

The Baldacci administration’s idea of merging the state corrections and county jail systems attempted to do that, but it has never been given a real chance to work.

It’s a truism of state government that there is no public outcry for spending on corrections, and the administration deserves credit for bringing forward a plan for an unpopular area of state spending.

But before this plan goes forward, the governor will have to explain why it jumped to the front of the line.