A 1992 survey (Green) showed that in the United States and Canada evangelicals make up both the largest and the most active group of Christians (surpassing both Catholics and Mainline or non-Evangelical Protestant groups).
http://en.wikipedia.org/wiki/Evangelicalism#United_StatesBecause evangelicalism lacks denominational structures or membership requirements, and because those who identify as evangelicals often have varying definitions of what that label means, it is difficult to count them. A 2003 Gallup Poll found that 42 percent of Americans self-identified as "born-again or evangelical," up from 36 percent in 1992.
Still, it appears certain that evangelicals will be key to the 2004 election for Bush. The Gallup Poll showed that in 1994, 42 percent of Republicans and 38 percent of Democrats identified as "born-again or evangelical." In 2003, the gap was up to 10 points, with 49 percent identifying as Republicans and 39 percent as Democrats. And the recent survey "American Evangelicals" showed that nearly seven in 10 white evangelicals are either Republican or lean GOP, while just 23 percent would vote or lean toward the Democrats.
http://www.religionlink.org/tip_040503a.phpAnd the Jesus Camp Trailer puts the makup at 25%. You can click on the ad on DU.
An estimated 70 million Americans call themselves evangelicals, and their beliefs have already reshaped American politics. In the last election, 40 percent of the votes for George W. Bush came from their ranks, and now those beliefs are beginning to reshape the culture as well -- thanks to a group of best-selling novels known as the “Left Behind” series.
http://www.cbsnews.com/stories/2004/02/05/60minutes/main598218.shtmlDominionist Influence in The U.S. Congress
2004 senate graph
One way to measure the political strength of dominionists is to study voting patterns of members of Congress. A recent amendment added to a bill in the U.S. House of Representatives, HR 2123, allows religious discrimination in Head Start hiring which is a serious blow to both religious liberty and civil rights. more The graph on the right shows how Representatives voted.
210 Republicans and 10 Democrats voted for the amendment. 9 Republicans, 186 Democrats and 1 independent voted against the amendment. This graph illustrates that dominionists reside overwhelmingly in one political party. Since the Republican Party has majorities in both houses of Congress, they set the agendas, chair the committees, and decide which bills will and won't come up for a vote.
Congressional scorecards from organizations such as the Christian Coalition, Family Research Council, and Eagle Forum also illustrate the strength of dominionists in Congress. Click here to view Senate Congressional scorecards from those three organizations as compared to the League of Conservation Voters, a consortium of environmental groups. You'll see an almost perfect inverse correlation -- the higher the scores from dominionist groups, the lower the scores on the environment. (The tables in the above link were provided by Glenn Scherer, October, 2004 - note: four Democratic Senators were campaigning for the Presidential Primary in 2004 and missed many votes which lowered their environmental scores substantially.)
http://www.theocracywatch.org/Theocracywatch.org is an especially good site if you want some more info.