Even as voters got some relief from ubiquitous election TV ads Wednesday, campaigns prepared for more of the same. Much, much more.

The Republican Governors Association announced Wednesday it would spend $4 million for GOP gubernatorial candidate Rob McKenna, much of it likely to buy airtime. Earlier this week, a campaign seeking to legalize marijuana put down $500,000, and an independent group supporting a gay marriage also bought time.

They were trying to get out in front of what promises to be an unusually frenetic sprint to the fall general election, when voters will face a ballot packed with big choices.

The open race for governor is rated the hottest in the country, and candidates for three open seats in Congress have proved a willingness to self-finance their campaigns.

U.S. Sen. Maria Cantwell is up for re-election. And Republicans kindle hope, however faint, of retaking the state House and/or Senate.

For the first time, voters will get a say on two weighty social issues — marijuana legalization and gay marriage — as well as charter schools and another Tim Eyman anti-tax measure.

And there's the race for the White House.

All of that translates into a rush for money, eyeballs and voters' attention spans. Democrats and Republicans alike worry that, by November, the competing campaigns will saturate TV and mail.

"My biggest fear is people tune out because they hear too much," said state GOP Chairman Kirby Wilbur. "A lot of trees will die for these races."

If there's an upside to saturation, it's voter enfranchisement. In 2008, turnout hit the high-water mark of 85 percent, said Secretary of State spokesman Dave Ammons.

The "amazing array" of ballot measures may help eclipse that record, even as the state voter rolls have risen to 3.7 million, he said. "We're hoping to match or exceed the 2008 turnout."

With Referendum 74, Washington is one of four states — along with Minnesota, Maryland and Maine — with same-sex marriage on the ballot.

No fewer than six political committees — including one set up by Seattle-based Cupcake Royale — have registered to raise money in support. Together, gay-marriage backers are reporting more than $5.5 million in contributions — almost 20 times the amount of their opponents.

What impact gay marriage will have on other races depends on whom you ask.

David Domke, chairman of the University of Washington Department of Communication, said gay marriage is a "wedge issue" for McKenna's Democratic rival, Jay Inslee.

"I'm interested that Democrats who were on the defensive on these cultural issues for so long are now on the offensive," said Domke.

Wilbur said it is "a slight gain for us," potentially drawing out traditional-values voters.

Vote on marijuana

He is more concerned about another measure on the fall ballot — Initiative 502, which would legalize, regulate and tax recreational marijuana use. That measure is popular with younger voters, who lean Democratic.

The I-502 campaign has raised nearly $3 million, enough to start a $1 million TV ad campaign. In its first ad, which just began airing, a somber, middle-aged woman declares, "I don't like it personally, but it's time for a conversation about legalizing marijuana."

The campaign picked the 2012 ballot because younger voters, who disproportionately favor legalization, turn out in higher numbers during presidential elections.

Opposition includes the Washington Association of Sheriffs and Police Chiefs and some medical-marijuana patients, who object to a DUI provision in I-502. Neither group has raised big money.

The Nov. 6 ballot is also a fourth attempt to allow charter schools. Early polling indicates it could be close this time around.

Supporters of the public but independent schools have already raised more than $3.4 million, including $1 million from Bill Gates and $600,000 from Wal-Mart heiress Alice Walton.

Those campaigns must squeeze into airtime likely to be consumed by several self-financing congressional candidates. Democrat Suzan DelBene spent $2.3 million of her own money for the chance to face Republican John Koster in the 1st Congressional District.

Presidential race

Democratic consultant Ron Dotzauer said presumptive GOP presidential nominee Mitt Romney is unlikely to campaign heavily in Washington, which Obama easily won in 2008.

Voters more likely will be inundated with ads for Inslee and McKenna, rated by Politico as the top governor's race in the country.

The Democratic Governors Association has spent nearly $1.8 million over the past 13 months on Inslee. The Republican Governors Association (RGA) decided "to put our chips in the pot" — $4 million worth — Wednesday after initial returns in Tuesday's primary showed McKenna trailing Inslee 43 percent to 47 percent, said the RGA's Mike Schrimpf.

The donation is the group's largest single commitment to a state race so far this election cycle, said Schrimpf.

In another sign of the party's commitment to the state, New Jersey Gov. Chris Christie will headline a rally Thursday in Bellevue for McKenna and other GOP candidates.

Dotzauer estimates the governor's race ultimately could cost $30 million, with piles of independent expenditures adding to heavy fundraising by the candidates.

"I think the money will still come in big, because it's been elevated to such a lofty position. And the Republicans believe they have the best candidate in a long, long time," said Dotzauer. "They're going to make sure he's fully fueled."

Staff reporters Theodoric Meyer, Brian M. Rosenthal, and Lornet Turnbull contributed to this report. Jonathan Martin: 206-464-2605 or jmartin@seattletimes.com. On Twitter @jmartin206.