With the governor and 161-8 vote by the House and Senate on its side, property tax relief through a homestead exemption seems a virtual done deal, at least in principle.

Now come the details, and there are a few devils to be worked out. The size of the tax break, the amount every homeowner gets to knock off the valuation, wavers between $7,000 and $7,500. The starting date, this year or next, remains in question. The precise mechanism — an exemption each homeowner subtracts from the local tax bill or a rebate check from the state — still is under debate.

The first two shouldn’t be all that hard to settle. The relief should be as much as possible — $7,500 in this case — given the extent to which property taxpayers have shouldered the burden of financing essential government functions. The program must start this year. Taxpayers have waited long enough.

The third, the mechanism, is tricky. Gov. King, an early advocate of a homestead exemption, prefers a method wherein the property owner pays the full amount to the town and gets a rebate check back from the state. Most legislators back an exemption right on the tax bill — the money never leaves the taxpayer’s hand — with the town getting the state reimbursement.

The governor is right to worry that money sent to municipalities as reimbursement for tax relief might get squandered on new spending and tax bills still might go up. That’s worth worrying about, but it’s also worth remembering that it is the state, not the towns, that has the well-deserved reputation as a reneger. Community corrections, tree growth; the list of broken state reimbursement promises goes on and on.

It should not be difficult to design a system that protects the taxpayer. For example, a new standard property tax bill could show last year’s valuation and mil rate, numbers for the current year and then a simple subtraction of the exemption to give the total due. If there’s one thing the average Mainer looks at pretty closely, it’s the property tax bill. And if the selectmen want to treat the town’s total of exemptions as found money, as leeway for the purchase of gold-plated bathroom fixtures, they get to deal directly with the local pitchfork-and-torch crowd.

The ultimate concern should be what happens if another legislature fails to fund a property tax relief program. Under a direct exemption plan, the property owner still gets the break and the town gets stiffed. With a rebate, the taxpayer takes the hit; the rebate check never gets mailed. It seems likely that towns and cities, organized through the Maine Municipal Association and with a daily presence in Augusta, would be the more diligent watchdog on a finagling future legislature.

The exemption plan also costs less to run. It is estimated that the extra step in figuring tax bills would cost about $700,000 to set up the first year and about half that thereafter, with the state required by law to cover 90 percent of the local expense. The rebate program, heavy in paperwork and postage, would cost about $1.8 million. That’s just too much money spent for no apparent reason.

Gov. King and the Legislature deserve praise for putting property tax relief at the top of the agenda and for getting it this close to reality. It must not fall victim to the question of whether the State House or the Town Office is more trustworthy. Although — no offense to the State House — we’ll put our money on the Town Office.