Supporters of two more initiatives — for charter schools and a two-thirds requirement for lawmakers to raise taxes — submitted more than 300,000 signatures for each on Friday, likely rounding out a November ballot that also will include gay marriage and marijuana measures.

Two more voter initiatives on Friday appeared likely to squeeze onto a crowded November ballot, as supporters of charter schools and a two-thirds requirement for lawmakers to raise taxes each submitted more than the required number of signatures to the Secretary of State’s Office.

If the signatures are verified, the initiatives will join four other ballot measures — including gay marriage and marijuana legalization — in an election also featuring presidential, gubernatorial and congressional races.

With an unusually busy election shaping up, turnout could eclipse the record, set in 2008, of 86 percent, said Dave Ammons, a spokesman for Secretary of State Sam Reed.

“It should be an interesting year,” Ammons said.

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Friday marked the deadline for backers of ballot initiatives to submit 241,153 valid signatures. Six measures would be slightly more than average.

Ammons said this might the most intense election for ballot initiatives since 1997. That year, voters also weighed six measures, including proposed laws regarding gun control, gay rights, medical marijuana and dental-hygienist supervision.

“We called it the guns, gay, grass and gums year,” he said.

But this election will have something that one did not: a slew of competitive candidate races.

Matt Barreto, a political-science associate professor at the University of Washington, predicted the gay-marriage and marijuana measures will increase turnout, especially among young voters who wouldn’t otherwise mail in a ballot.

That could help Democrat Jay Inslee and hurt Republican Rob McKenna in the governor’s race, Barreto said.

Other analysts have speculated that the wide array of expensive campaigns could squeeze some donors. For example, the state teachers union is expected to put a lot of money into fighting the charter-schools initiative — money that won’t go to the union’s preferred gubernatorial candidate, Inslee.

The two initiatives for which supporters turned in signatures Friday have been considered by voters before.

In the case of charter schools — free and public schools that operate independently of traditional districts and use unconventional techniques — voters have rejected them three times (1996, 2000 and 2004).

While the schools sometimes have proved more effective than traditional schools in the 41 states where they exist, opponents criticize their use of nonunion teachers and argue that money shouldn’t be diverted from traditional schools.

Initiative 1240, sponsored by several education advocacy groups, would authorize 40 charters. Backers turned in about 350,000 signatures.

The two-thirds requirement for tax increases, on the other hand, has won voter approval four times. But the Legislature has repeatedly repealed it, which is allowed after two years.

In addition, it was found unconstitutional in May by Superior Court Judge Bruce Heller in a decision that is likely to be reviewed by the state Supreme Court.

The latest iteration of the measure, I-1185, is sponsored by initiative activist Tim Eyman, who turned in about 320,000 signatures.

Both measures already have attracted strong financial backing: I-1240 has generated contributions of more than $2 million, mostly from billionaire technology executives, while I-1185 has raised nearly $1 million, mostly from a Washington, D.C.-based beer lobbying group and the oil industry.

But they’ve also drawn stiff opposition. The state teachers union has promised a fight on charters, and a group of civic leaders, including state Rep. Reuven Carlyle, D-Seattle, has announced a campaign to oppose Eyman’s measure.

Two other high-profile measures have made the ballot: Referendum 74 asks voters whether to affirm a recent law allowing gay marriage; Initiative 502 seeks to legalize, regulate and tax recreational use of marijuana.

If approved, both would be firsts for the U.S. — recreational marijuana is illegal everywhere now, and gay marriage is allowed in six states but has never been approved by voters.

Two constitutional amendments, regarding use of state bond debt and investments by two public universities, also will be on the ballot.

Brian M. Rosenthal: 206-464-3195 or On Twitter @brianmrosenthal.