The number of religious advocacy groups in the nation’s capital has more than tripled since the 1970s, with conservative groups seeing the biggest growth, according to a new report.

Together, faith-based lobbying and advocacy groups spend $390 million a year to influence lawmakers, mobilize supporters and shape public opinion, according to the report, released Nov. 21 by the Pew Forum on Religion & Public Life.

The report reflects shifting fortunes in religion and politics: the rise of the religious right 35 years ago, the decline of mainline Protestant churches and the outsized presence of the Roman Catholic Church.

Conservative groups have seen some of the largest budget increases; the National Organization for Marriage, which has racked up a string of victories in its fight against gay marriage, saw its budget grow from $3.2 million to $8.5 million between 2008 and 2009.

There are now as many Muslim advocacy groups as mainline Protestant groups, and evangelicals and Roman Catholics constitute a strong 40 percent of religious lobbyists in and around Washington.

“Religious advocacy is now a permanent and sizable feature of the Washington scene,” said Allen Hertzke, a political scientist at the University of Oklahoma and the primary author of the report.

Hertzke's report surveyed 211 religious advocacy groups, ranging from the U.S. Conference of Catholic Bishops to the American Jewish Committee to the American Friends Service Committee (the Quakers).

The groups surveyed by Pew have grown from 67 in the 1970s, and Hertzke conceded that figure is probably an undercount. “We don’t claim to have gotten all of them,” he said.

Using financial reports from public tax forms, Hertzke said the biggest spender is the pro-Israel American Israel Public Affairs Committee, which spent $87 million on advocacy in 2008. U.S. Catholic bishops were second, with $26.6 million spent in 2009, followed by the Family Research Council, with $14 million in 2008.

The biggest winners and losers ― at least as judged by their budgets ― reflect the turbulent politics of the last few years:

  • As the Obama administration took office and the recession worsened, the progressive PICO National Network boosted its budget by $100 million to advocate for the poor, health care reform and other social justice causes.
  • The nation’s Roman Catholic bishops boosted their advocacy budget by $1.4 million as fights heated up against Obama’s health care overhaul and same-sex marriage.
  • The Muslim American Society boosted its budget by 29 percent, and the American Islamic Congress by 41 percent, between 2008 and 2009 as Islamophobia intensified in the form of opposition to mosque building and the so-called Ground Zero mosque.

Many religious advocacy groups are relatively modest operations; the median annual budget was about $1 million for the 131 groups where financial data were available.

Most groups split their portfolios between domestic and international issues, with a plurality (42 percent) representing individual voters or constituents. Just 15 percent represent religious bodies such as denominations.

Despite their presence in the nation's political capital, only a small sliver of groups ― 7 percent ― have formed political structures that are able to advocate for or against particular candidates. The vast majority of groups are tax-exempt and prohibited from partisan politics.

That surprised Maggie Gallagher, co-founder of the National Organization for Marriage, who traced the rise in religious advocacy to the political ascent of conservative Christians in the late 1970s and 1980s.

“Not everyone has to be involved in politics, but if you are going to claim to want to be involved in politics, you need to build institutions to accomplish your political goals,” said Gallagher, who has been targeting candidates who support same-sex marriage.