"another $500 million regressive sales tax increase"
The Official Local Voters’ Pamphlet for the primary election in King County includes statements for and against Proposition 1, which would impose a 0.1% increase in the sales tax in order to fund arts, science and cultural enrichment programs.
The statement against Proposition 1 states, “it is unwise and inequitable to impose another $500 million regressive sales tax increase on overburdened King County taxpayers.”
The interesting thing about this statement is that one of the co-authors is state Senator Dino Rossi (45th LD), a Republican who ran for governor. Republicans are, with few exceptions, adamantly opposed to fixing our regressive tax system. In the latest session of the legislature, they refused to agree to a capital gains tax and instead insisted on raising real estate taxes to fund education. Real estate taxes are more regressive than a capital gains tax, though not as regressive as a sales tax.
It’s disingenuous for politicians who oppose progressive taxation to use an argument about regressivity to attack a ballot initiative that increases the sales or real estate tax.
At least they acknowledge that the problem exists.
I note, by the way, that the legislature, including Republicans, voted, in 2015 to raise the regressive gas tax by 11.9 cents.  See http://www.thenewstribune.com/news/politics-government/article43025553.html and Gas tax increases by 7 cents in Washington state.