OLYMPIA — The Senate on Monday passed a budget plan that relies, in part, on modifying a class size ballot measure and asking voters if they agree with the decision.

The $38 billion, two-year budget passed the Republican-controlled chamber on a party-line 26-23 vote. It doesn’t include any new taxes, mostly relying on existing revenue, fund transfers and redirecting tax income from recreational marijuana.

The chamber’s main budget writer, Republican Sen. Andy Hill said that the budget focuses on education and “lives within our means and is sustainable.”

Lawmakers this year are tasked with writing a new two-year operating budget for the state under the shadow of a Supreme Court -ordered requirement to put additional money toward the state’s education system.

There are differing ideas between the politically divided chambers on how best to do that, with Democrats seeking more revenue and Republicans saying new taxes are not needed.

Before taking a final vote on the Senate plan, the chamber approved a bill to make changes on Initiative 1351, which reduced class sizes for all grades. The cost to pay for the measure was in the billions, and the Senate bill only pays for reductions for kindergarten through third grade. That change would go to voters for their approval or rejection.

Senate Democrats decried that decision, saying that if voters in November reject the lawmakers’ decision to change the initiative, the budget will immediately be out of balance.

“This budget is built on magical thinking, a kind of house of cards if you would,” said Sen. Karen Keiser, who focused on the decision to balance the budget on an assumption that voters will agree with lawmakers’ decision on changing I-1351. “What if the voters say no? Then this entire house of cards falls apart, it collapses.”

The Democratic-controlled House passed its own plan last week, though it hasn’t yet voted on other bills that will pay for the plan, including one that creates a capital gains tax and others that seek to close some tax exemptions. However, House Democrats and Senate Republicans will need to work to try and negotiate a final plan before the 105-day legislative session ends later this month.