Once upon a time, restless billionaires who needed a hobby bought themselves a sports team. Now, since Citizens United paved the way for endless donations, they buy Republican presidential candidates, too.

For tonight’s GOP presidential debate, the predictable media line will boil down to “Does this hurt or help Trump?” The media will always reduce the election to the horse race, and they’re predicting tonight will be a free-for-all.

But as citizens, you might ask a different question: Cui bono? Who stands to gain? Are these Republican candidates hired mercenaries for outside interests? Let’s take a look.

We’ll start with Ben Carson, who was the Tea Party flavor of the month for a while. Just 197 disclosed donors gave the primary-campaign maximum contribution of $2,700 in his second quarter — not a lot. Presumably through personal relationships, the good doctor got a lot of donations from medical personnel. Carson raised most of his money last quarter through direct mail, which means his donor support is diffused. We don’t see special interest groups in his finance reports. From most accounts, his heart isn’t really in the race — and he’s running out of money.

Then there’s Ohio Gov. John Kasich. Kasich is heavily backed by Chamber of Commerce and Club for Growth types. (He has one billionaire donor, who mostly gives to Democrats.) What does Kasich believe in? Cutting government services. He did strongly defend expanding Medicaid in Ohio, but make no mistake: he’s a deficit hawk who wants a balanced budget amendment that will dismantle government. He only looks moderate compared to most of the other candidates.

Which funders are behind Sen. Marco Rubio’s baby face? He’s very eager to serve the agenda of the GOP donor class. Rubio has written legislation expanding the use of the H-1B visa, sometimes called “legal servitude” – which could account for the backing of billionaire Paul Singer, and Las Vegas billionaire Sheldon Adelson. It’s a major issue for both Adelson and Norman Brauman, Rubio’s biggest Florida funder.

Former federal prosecutor and New Jersey Gov. Chris Christie looked a lot more like a winner four years ago, when donors were begging him to run. Then came Bridgegate, and Christie’s image went from Mr. Straight Talk to Mr. Talk From Both Sides Of His Mouth. He gets backing from billionaires with gambling interests like casinos and on-line poker. (Sheldon Adelson backs him, too.) In spite of the sleaze factor and his willingness to throw principle to the winds, Christie (like Marco Rubio) is essentially an establishment kind of guy.

Which leads us to our last GOP contender. Who is still backing Jeb Bush, who was once considered the front-runner? Establishment types, the same kind of moneyed interests who backed Mitt Romney. What do they want? Business as usual. They are likely to get it.

If you don’t have cable, a livestream of the debate is available online at FoxBusiness.com starting at 6 p.m. Eastern.