Further, a church, as a 501(c)(3) organization, may also engage in a certain amount of legislative lobbying – including paying a 501(c)(4) like NOM to lobby on its behalf – with the limits defined as an “insubstantial” percentage of annual expenses. One very cost-effective way to get around these limitations, as the Mormon Church demonstrated with Prop 8 in California, is to spend a relatively small amount of money encouraging its members to give directly to NOM (or another group).

These arrangements between 501(c)(3) and 501(c)(4) organizations are quite common, including in Vermont (VPIRG, Vermont League of Conservation Voters, the ACLU, etc.). A 501(c)(3) can set up 501(c)(4) and vice versa, and it’s all quite legal and proper – so long as the organizations are kept legally distinct and they operate under clearly defined financial agreements. The fact that a church is involved as the 505(c)(3) is legally irrelevant. The issue isn’t one of church-state separation, but of tax-deductibility under a statute passed by Congress long ago.

What a church – or any other 501(c)(3)) – cannot lawfully do is to support or oppose candidates for public office. A number of churches have openly flouted this stricture, but as you note little has been done to enforce the law, especially during the Bush years. (Not surprising, as most violators have been Catholic and rightwing churches expressing opposition to Democratic candidates, and Democrats, bless their timid little hearts, have been reluctant to forcefully engage the issue.)

Whatever its relationship with NOM, the only way that the Mormon Church’s legal status could be “endangered” is if they employ lousy lawyers and sloppy accountants. However, the Church’s social status is another question.