Sen. Ed Murray, of Seattle, said he'd like to see voters approve the tax along with a package of reforms supported by a Republican-leaning coalition in the Senate. Murray said both sides need to come together on a larger compromise.
Murray's proposal adds a 5 percent tax on capital gains, but it would exempt the first $10,000 in gains for individuals. Murray projected that a small fraction of voters would be impacted by the tax.
As the state prepares to set up the system, Murray would temporarily extend a beer tax and a business tax paid by doctors, lawyers and others until the end of 2015.
"It will take some time to get this up and running," Murray said.
The proposal also has a difficult path to get out of the Senate, or even a committee hearing. Now that Murray and Democrats are in the minority, he will need to persuade a Republican-dominated coalition to join the effort. Republican lawmakers have said the state needs to focus on having government live with the revenue it already has.
Republican Rep. Gary Alexander, a budget writer in the House, said the state needs to focus on simply funding education first and not focusing on creating a new tax.
"We don't need it," Alexander said.