HELENA — A Republican proposal requiring the state to spend nearly all of its future budget surpluses on property tax relief won preliminary House approval Friday on party lines.

The bill by Rep. Roger Koopman, R-Bozeman, initially failed on a 50-50 vote, but passed 51-49 after the lone Republican who voted against it, GOP Rep. Gary MacLaren of Victor, asked that it be reconsidered and changed his vote.

All of the House Democrats opposed the measure. A final vote is scheduled Saturday.

The bill sets aside 6 percent of that budget year’s revenue for emergencies, but requires any money over that amount to be given back to property taxpayers.

Any money left over after the property tax reductions would be set aside for contingencies and income tax refunds.

Koopman and other conservatives said it’s only fair to give taxpayers their money back when the government has too much of it.

“It’s the taxpayers’ money. They should get it back,” said House Majority Leader Michael Lange, R-Billings.

Democrats said the proposal primarily benefits the wealthy and called it foolhardy to guarantee tax cuts years from now when the state’s financial picture could sour.

“This bill is forever,” said Rep. Jill Cohenour, D-East Helena.

Rep. Franke Wilmer, D-Bozeman, also challenged the GOP assertion that state government has grown in recent years, saying “government has not expanded relative to the context of our own ability to increase our own wealth in the state of Montana.”

“We, in the long run, have not had an increase when we put it relative to things like population growth and inflation,” she said. “We have not grown.”

Koopman said a budget surplus shouldn’t be an excuse to expand state government. To keep lawmakers from being tempted by any extra money, it should be returned to the taxpayers who put it there, he said.

“This really is an act of good faith toward the taxpayers of this state,” he said.

The bill is House Bill 315.