Let's start on the Republican side. Fully 87 percent of those who identify themselves as Republicans or Republican-leaners are white in 2012 Pew polling while just 5 percent are Hispanic and four percent are black.
When it comes to the religious affiliations of GOPers and GOP leaners, the largest bloc are white evangelical Protestants who comprise roughly one in every three Republicans (34 percent). Here's the full GOP religious affiliation chart via Pew:
Now, for the Democrats. As expected, the party is more racially diverse. Sixty-one percent of Democrats and Democratic-leaners are white while 21 percent are black and 10 percent are Hispanic.
When it comes to religious affiliation, the biggest group of Democrats -- roughly one in every four -- identify as religiously unaffiliated. The next largest bloc are black Protestants who comprise 16 percent of all Democrats and Democratic leaners in Pew polling.
Here's the full breakout of Democratic religious affiliation by party ID:
What does the data tell us? Yes, white evangelical voters comprise a major bloc of registered Republican voters. And, yes, minorities and those with no religious affiliation are a major portion of the Democratic voting base.
Yet, neither white evangelicals nor religiously unaffiliated voters make up even close to a majority of the registered voters in their respective parties -- meaning that the stereotypes of the two parties are, not surprisingly, a bit overblown.