U.S. Sen. Maria Cantwell doesn't have a challenger yet in her re-election bid next year, but she's the target of a new campaign, nonetheless.

Two prominent lobbying groups based in Washington, D.C., are joining to put her on the spot on tax issues, and one of them is kicking off TV and radio ads today.

The American Family Business Institute, which opposes the estate tax, is launching a series of commercials urging Cantwell, a Democrat, and senators in five other states to vote to permanently repeal the federal tax next month in Congress.

The institute's executive director, Dick Patten, is a longtime Seattle businessman who earned his political spurs in 1981 when he led Initiative 402, which effectively repealed the state's estate tax.

In 2002, Patten helped defeat Referendum 51, which would have raised the gas tax to help pay for transportation projects.

He wouldn't say how much his organization is spending on the anti-tax campaign.

The American Family Business Institute has allied with Americans for Tax Reform and its director, Grover Norquist. With an ability to reach some 10 million voters nationally, Americans for Tax Reform is considered among the nation's fiercest Republican political strategists and played a role in defeating Senate Democratic Leader Tom Daschle of South Dakota last year.

"The death tax is a terrible tax that cripples small, family-owned businesses," Patten said. "We want Maria to vote the right way on this when it comes up."

Senate Republicans plan to introduce a bill this month to either repeal or significantly cut the estate tax. A permanent repeal passed the House in April.

Cantwell voted with Democrat Sen. Patty Murray against a permanent repeal of the tax in 2002. But spokeswoman Charla Neuman said Cantwell supports a Democratic proposal to eliminate the tax for family businesses and farms worth under $100 million.

"This group is clearly making this a partisan, not a policy issue," Neuman said, referring to the American Family Business Institute.

Josh Kahn, the organization's spokesman, called the estate-tax proposal that Cantwell supports "a Democratic shield. The rules for meeting that threshold are too complex for most businesses."

Cantwell is expected to meet with Patten's American Family Business Institute in two weeks, when she'll be asked to commit to a permanent repeal, not specific reforms.

She also has discussed the issue with Frank Blethen, the publisher of The Seattle Times and a well-known opponent of the estate tax. Members of the American Family Business Institute have attended Blethen's annual estate-tax summit in Washington, D.C. But Blethen has not contributed to the group, both he and Patten said.

Patten, 52, said he intends to push an initiative next year that would overturn the state estate tax passed this spring by the Legislature and signed into law by Gov. Christine Gregoire.

If successful, the initiative would share the November 2006 ballot with Cantwell's re-election effort.

"That will make it very interesting for her, and for the legislators in Olympia, I promise you," Patten said.

His co-sponsor on the ads is the Free Enterprise Fund, a new pro-business lobby founded by Stephen Moore. He is the former president of the Club for Growth, which raised nearly $20 million for Republican candidates in 2004.

Patten, Moore and Norquist will make a formidable trio. Norquist has made taxes a high-profile issue in many campaigns.

Norquist also wants Cantwell to vote to abolish the 3-cent excise tax on phones that has been in existence since the Spanish American War in 1898.

"The tax issue is a central issue and Cantwell and politicians ignore it at their peril," Norquist said.

The new TV ads depict veterans of World War II, including a hero of the original "band of brothers" in Europe, while a voiceover talks about the impact of the estate tax on them.

"They paid taxes all their lives ... but now the IRS hits this greatest generation with an unjust double tax ... the death tax," the ad says. "Tell Maria Cantwell to change her vote on the IRS death tax. It's wrong and she knows it."

Cantwell's spokeswoman, Neuman, responded: "Ask the men in the ads if any of them own land worth more than $100 million. If not, then I believe Maria has voted to repeal the tax for every one of them."

What would Patten do if Cantwell agrees to support an estate-tax repeal?

"We've already filmed a version of the ad asking voters to call and thank her," he said.

Alicia Mundy: 202-662-7457 or amundy@seattletimes.com