In his rise from the House's second-youngest member to the 2012 presidential ticket, Paul Ryan has relied on the finance and insurance industries, as well as his Wisconsin background, to become a rainmaker who should provide the Romney campaign with a valuable fundraising asset.

Since his first re-election campaign in 2000, the biggest funders of Ryan's political career have been financial firms, insurance companies, and wealthy Wisconsin companies and individuals, which have helped him amass a $4.5 million war chest, the largest in the House.

The money behind Ryan's political career is best encapsulated by his biggest source of cash: Northwestern Mutual. As a Milwaukee-based insurance company that also offers financial services, it is all of Ryan's biggest political backers rolled into one. The company and its employees have given him nearly $90,000 over the years, according to the Center for Responsive Politics.

But before he became the country's leading advocate for privatizing Social Security and shrinking Medicare (and therefore a favorite of insurance companies), Ryan relied on homegrown support. Because of his family's construction business, Ryan Inc., construction groups were Ryan's primary financial backers in the beginning, the largest being the National Association of Home Builders and the Carpenters and Joiners Union, each of whom have given more than $50,000 over his career, according to CRP.

Midwestern groups such as the National Beer Wholesalers Association, based in Milwaukee, and companies based out of nearby Chicago, such as Abbot Laboratories and Bank One, also backed him early on.

As he ascended the ranks, his construction backers gave way to large financial groups such as Credit Suisse Group, National Association of Insurance and Financial Advisers, and the American Bankers Association. After becoming the top Republican on the powerful Budget Committee in 2007, when Ryan's budget plans became more widely known, insurance and healthcare groups became a substantial new source of political cash. Thus far in the 2012 cycle, all but eight of Ryan's 20 biggest backers are in the financial, insurance, or health sectors, CRP data shows. Most are financial groups like Elliott Management, the hedge fund that's also a big giver to Romney's campaign. Other familiar companies like Goldman Sachs and UBS are also big contributors to Ryan, who frequently criticizes the Dodd-Frank Act that regulates Wall Street and voted for the TARP bill that bailed out Wall Street banks.

Ryan brings in cash from across the country, and thus far in the 2012 cycle, nearly 70 percent of his contributions have come from outside Wisconsin. Chicago and Milwaukee are his most lucrative areas, but he's also raked it in from surprising areas like Florida, which is actually his third-most generous state. This widespread appeal could help the Romney ticket, which raised $3.5 million after announcing Ryan would be its veep, see a permanent bump in fundraising despite both men attracting money from many of the same places.

The vice presidential nominee's campaign finance record is not without some minor controversy. To begin with, he has long been a favorite of the libertarian billionaires Charles and David Koch. Before entering Congress, Ryan worked with a conservative group that would eventually merge with a Koch brothers' group to become FreedomWorks, a leading sponsor of the Tea Party movement. Their mutual interests in libertarianism could explain why the private energy corporation Koch Industries has given Ryan more than $65,000 over his career. The Koch brothers have promised to funnel $400 million through outside groups to defeat President Obama this year.

Ryan's wife, Janna Little Ryan, has also entangled Ryan in some potential conflicts of interest. Her family owns stakes in land and energy companies in Texas and Oklahoma, and according to her husband's personal financial forms, the couple has at least $800,000 worth of holdings in those companies. An investigation by the Daily Beast last year found that those companies would receive $45 billion in tax breaks and subsidies under Ryan's proposed budget.

Mrs. Ryan also spent a decade in Washington as a corporate lobbyist, where she worked primarily at PricewaterhouseCoopers. Not only is PricewaterhouseCoopers one of her husband's largest sources of contributions, but so are two of her clients while working there: United Parcel Service and Blue Cross Blue Shield. Altogether the three companies and their employees have given Ryan more than $150,000 over the years.

Then there's Ryan's connections to a Wisconsin businessman, Dennis Troha, who with his family gave Ryan nearly $60,000 in contributions from 1999 to 2005, according to the Washington Post. Troha was simultaneously trying to open a large Indian casino in Ryan's district and lobbying for legislation giving his trucking company special hauling privileges. To do so, Troha enlisted Ryan, who made phone calls to federal agencies and pushed for the truck legislation on Troha's behalf.

In 2007, Troha was indicted on charges of funneling illegal campaign contributions to Wisconsin politicians to advance his gaming and trucking interests, and Ryan was the only politician named in the court documents when Troha's associate pleaded guilty to the scheme. Ryan would later donate the equivalent of Troha's contributions to a local Boys and Girls Club.