This is the latest installment in a series of reading guides on 2012 presidential candidates. Here are the other guides.

The Basics

Rick Santorum's strong showing in the Iowa caucuses has vaulted him from obscurity to presidential contender. Just a few months ago, Santorum barely merited a mention as Republican voters fell in and out of love with Rick Perry, Herman Cain and New Gingrich.

So who is this darling of the evangelical movement?

Santorum, 53, is devout, hawkish, competitive and polarizing. Social conservatives praise him for his hardline positions. He opposes abortion, even in cases of rape and incest, believes gays should not be allowed to marry, and has said he would bomb Iran's nuclear sites if they are not opened to international inspection. Evangelicals applaud the prominence he gives to his faith. Liberals decry him for many of the same reasons.

Santorum's path along the campaign trail has been unusual by standards of modern politics. A recent New York Times profile of the candidate noted that his Iowa operation lacked a campaign headquarters, a speechwriter, advance team or advertising budget. The Times said Santorum set out to win the "old-fashioned way, through shoe-leather politicking." That involved lots of moving around. In the months leading up to the Iowa caucus, he visited all 99 counties in Iowa, often traveling by himself or with a single press aide.

The Background

If you want more than his official stance on the issues, you can take a look at NPR's recently listed the Five Things You May Not Know About Rick Santorum, including the fact that he jokes about spending his childhood in public housing, has spoken against programs that would pay for community service, and has two nieces.

A long Des Moines Register profile describes Santorum's journey from an ambitious young staffer and law student to 32-year-old U.S. representative of Pennsylvania and, four years later, senator. Here's a timeline of some key events in his life and more on his voting history. He helped author a landmark welfare reform act that gave states more responsibility for administering welfare and put time limits on how long a person could receive assistance. The bill passed with bipartisan support. Santorum was one of the Gang of Seven, a group of freshman Republicans that exposed several congressional scandals. He was elected to the Senate in 1994 and served two terms before losing by 18 points to Democrat Bob Casey in 2006. Since then he has worked as a lawyer and as a commentator on Fox News, a gig that ended when it became clear he was running for president.

Santorum has steadily gained popularity with the Christian conservative base. TIME magazine listed him as one of America's "25 Most Influential Evangelicals," and he recently won the endorsement of several prominentevangelical leaders. This New York Times story from 2005 is perhaps the deepest look at Santorum the Believer, whom a former aide once called "a Catholic missionary who happens to be in the Senate."

He is "at home on the far right of the Republican spectrum" as a profile in the Los Angeles Times puts it. Santorum fiercely opposes gay marriage, calling it a threat to the traditional values of this country. As a senator he fought for anti-abortion legislation -- which is why he calls himself the only Republican candidate with a track record on the issue.

Santorum is well known for his colorful and often controversial comments. The website Santorum Exposed keeps a list of his "greatest hits." Here are just a few:

"It's amazing that so many kids turn out to be fairly normal, considering the weird socialization they get in public schools." July, 2005.

"I think it has, as we've seen, very harmful long-term consequences for society. So birth control to me enables that and I don't think it's a healthy thing for our country." July, 2005.

"A lesbian woman came up to me and said, 'why are you denying me my right?' I said, 'well, because it's not a right.' It's a privilege that society recognizes because society sees intrinsic value to that relationship over any other relationship." May, 2011, explaining his view on gay adoption.

Santorum wrote in the National Review that two texts -- the Declaration of Independence and the Bible -- have shaped his guiding beliefs in "the dignity of every human being:" He and his wife Karen have seven children, all of whom they have home-schooled.

Santorum has called for public schools to teach students about the possibility that God, not evolution, was the moving force in the creation of the human species. In 2002 he wrote in the Washington Times that "intelligent design is a legitimate scientific theory that should be taught in science classes."

Controversies

In 2003 Santorum gave an interview to the Associated Press in which he equated homosexuality with bestiality and pedophilia. In protest, one gay activist spread a fake, vulgar definition for his last name all over Google. Santorum sued Google (he lost).

In one of the GOP debates this September, Santorum sparked another wave of criticism for his remarks on the military's policy of banning gay soldiers, known as "Don't Ask, Don't Tell." (He called the recent repeal of those rules "tragic"). He didn't speak up when audience members booed a gay soldier. The gay rights group GOProud demanded an apology. None was issued.

Following the Money

Santorum has raised far less than other Republican candidates, taking in only $1,286,975, according to his page on OpenSecrets.org. That's less than half as much as the next nearest candidate Newt Gingrich, who has raised about $2.9 million. Most contributions came from Santorum's home state of Pennsylvania, according to this New York Times interactive fundraising guide, which you can use to compare Santorum to other candidates.