The six prosperity gospel ministries under scrutiny by Republican Sen. Charles Grassley are a tough group to take on. The televangelists are veterans at outmaneuvering opponents, and in this case are even getting support from their critics.

Religious groups who consider the prosperity gospel a rip-off still see the inquiry as a potential threat to church independence if it ends with new tax rules for all ministries.

The investigation also has the potential to alienate Christian conservatives at a time when the GOP can least afford to do so — ahead of a presidential election in which no prospective Republican nominee has shown he can mobilize the Christian right nationwide.

"I was amazed that Grassley took this on knowing this likely will stretch into next year," said Bill Martin, a Rice University sociologist and author of "With God on Their Side: The Rise of the Religious Right in America."

Grassley, the ranking Republican on the Senate Finance Committee, is looking at whether the televangelists' salaries and benefits exceed IRS limits for nonprofits. He has spent years reviewing the finances of tax-exempt organizations.

The Iowa senator says he is simply enforcing the existing tax rules. But that's little comfort for the many Christian conservatives who loathe the IRS. Some religious leaders have been trying unsuccessfully for years to overturn IRS restrictions on political activity for their groups.

Long before Grassley announced his inquiry, critics inside and outside the Christian community had been targeting televangelists for how they raise money, then spend what they collect. The prosperity gospel teaches that rewards come in this life to people who are approved by God. The more money that followers give to the ministries, the greater the return, according to the philosophy.

Hank Hanegraaff, president of the Christian Research Institute, a well-known evangelical group in Charlotte, N.C., has written and spoken extensively against prosperity teaching. The Trinity Foundation, a Christian group in Texas, is so dedicated to taking down the ministries, it dives into their Dumpsters to get evidence against them.

Yet, detractors have failed to slow the groups.

The six ministries under review collectively receive hundreds of millions of dollars in donations each year. While the preachers vary in their personal wealth, they are positioned to hire the best lawyers and public relations advisers in any showdown with the government.

The groups aren't legally required to provide the documentation the senator requested, and only one — Joyce Meyer Ministries of Fenton, Mo. — pledged full cooperation. Two others — Georgia megachurch pastors Creflo Dollar and Bishop Eddie Long — aren't complying.

Kenneth and Gloria Copeland of Texas turned over some materials, which Grassley is reviewing. The two remaining ministries — Benny Hinn of Texas and Randy and Paula White of Tampa — have had contact with Grassley's office, but haven't said whether they will answer all his questions.

Grassley has faced organizations with deep pockets before, but the preachers have another advantage: an unparalleled ability to defend themselves to their constituents.

The ministries broadcast around the country and the world — often daily — and have taken full advantage of the Internet age to communicate with followers. The preachers not only spread religious beliefs, but also a worldview. And from their perspective, Grassley's investigation can be seen as another instance of persecution in a society that doesn't accept them.

Paul Crouch Jr., son of the founder of the Trinity Broadcast Network — which is not under review, but broadcasts some preachers who are — has called Grassley's investigation an "inquisition" that amounts to "spiritual warfare."

Crouch drew a parallel between resisting the senator and fighting off Nazis.

Grassley tried to blunt this kind of criticism by emphasizing his own spirituality, as a dedicated, churchgoing Baptist, but the approach has backfired.

Religious leaders complained that Grassley created a perception that his investigation pits one religious view against another. Some critics noted that Baptists and other evangelicals have deep theological differences with Pentecostalism, which gave rise to the prosperity gospel.

Grassley has repeatedly insisted that his investigation is not about doctrine, but whether the ministries are playing by the rules.

The televangelists insist that they are. But they might never have to prove it.

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