Rick Santorum seems undaunted by money. Other people’s money, that is.

The former Pennsylvania senator was heavily outspent when he ran for the Republican presidential nomination in 2012. He may face a similar spending shortfall now that he’s declared his candidacy for the 2016 race. With Santorum in the hunt, GOP donors will have more than a dozen candidates to choose from heading into the primaries next year.

Santorum raised about $22 million during the 2012 race—less than he pulled in when running for reelection to the Senate in 2006 (when he lost), according to the Center for Responsive Politics. A so-called super PAC supporting Santorum's presidential bid raised $8.5 million more and spent most of that running ads on his behalf. Still, the ultimate Republican nominee in 2012, Mitt Romney, raised about 15 times as much money as Santorum. That sort of funding disadvantage could be even more acute in 2016, since at least four other declared or likely candidates—Jeb Bush, Scott Walker, Marco Rubio and Ted Cruz—have already locked up some of the richest contributors.

In the past, however, Santorum has generated support from a few key money mavens he'll no doubt lean on this time around, including:

Bill Doré, the Louisiana businessman who made his fortune constructing offshore oil and gas facilities. In 2012, Doré was the top contributor to Santorum’s super PAC, the Red, White & Blue Fund, giving $2.25 million. Dore is usually mum about his political donations, and hasn’t said whether he plans to support Santorum in 2016. But he’s a versatile donor who gave relatively small sums to Mitt Romney in 2012 at the same time he was heavily backing Santorum. So he may spread his money around again in 2016.

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Foster Friess, the wealthy Wyoming investor, who contributed $2.1 million in 2012 to Santorum’s Red, White & Blue super PAC. Friess has donated to many Republicans. Between 2011 and 2014, he gave $124,600 to Wisconsin Gov. Scott Walker, who’s likely to compete against Santorum for the 2016 GOP nomination. He made four-figure contributions during recent years to Ted Cruz and Rand Paul, also running for the nomination. Yet Friess, who describes himself as “born again,” seems especially fond of Santorum’s firebrand politics and has said Santorum’s his man in 2016.

Annette Simmons, widow of billionaire Texas businessman Harold Simmons, who died in 2013. She gave Santorum’s super PAC $1.2 million in 2012.

Catholic activists, such as Timothy Busch, a California hotelier, and Terence Castor, a San Diego businessman who has funded efforts to ban gay marriage. Santorum is Catholic and touts his religious beliefs as a central element of his political persona.

Small donors. About half of Santorum’s campaign budget in 2012 (not including the super PAC), came from individuals who contributed $200 or less. Just 18% of Romney's funding, by contrast, came from small donors. Santorum’s supporters tend to be anti-abortion conservatives who say religious and moral beliefs are a candidate’s most important traits.

Santorum lost at least one important donor this year: John M. Templeton, the surgeon and philanthropist who died in May at age 75. Templeton gave Santorum’s super PAC $265,000 in 2011 and 2012. A thinly financed campaign may be a bit thinner in 2016.

Rick Newman’s latest book is Liberty for All: A Manifesto for Reclaiming Financial and Political Freedom. Follow him on Twitter: @rickjnewman

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