Bernie Sanders (left) and Hillary Clinton during the Democratic presidential candidates debate on Thursday. (Reuters/Mike Segar)

In the one-on-one format of Thursday's Democratic debate, Hillary Clinton and Bernie Sanders spent much of the first hour trading and landing punches. (Figuratively.) Sanders landed solid blows with his well-honed argument about the role of money in politics and how that keeps Wall Street powerful. He argued that he, not Clinton, would take Wall Street on.

Clinton rebutted by implying that Wall Street was more afraid of her than of him.

"You've got hedge fund billionaires aligned with Karl Rove," Clinton said, "running ads against me to try to get Democrats to vote for you. I know this game. I'm going to stop this game."

Later, she continued. "I think the best evidence that the Wall Street people at least know where I stand and where I have always stood is because they are trying to beat me in this primary. They have collected and spent as much as $6 million on these ads. Hedge fund billionaires, Karl Rove, another billionaire, jumped in."

"Why are they doing that?" she asked. "These are guys who try to make smart investments. They know my record, they know me, they know that I say what I believe and I will do it. And I also have a pretty good understanding about how to stop them."

The implication? Wall Street wants Clinton to lose because they think she'd be tougher on them than would Sanders. That's worth evaluating.

The ad Clinton refers to above was run by American Crossroads, a group founded by Karl Rove.

You'll notice that the tone is hardly one that embraces Wall Street. It explicitly uses Clinton's past ties to Wall Street against the former secretary of state.

The industry that gave the most to Crossroads this cycle was Wall Street, according to the Center for Responsive Politics. That's people who work on Wall Street, not Wall Street firms. But it got money from other industries, too. In 2014, it raised $9 million from Wall Street.

Priorities USA, a PAC supporting Clinton, estimated that $6 million was spent by "GOP Special Interests" against Clinton, including on that spot. That's a broader universe of people than "Wall Street," and includes efforts like this, by a group called Future45:

Among the donors to that group are hedge fund billionaires Ken Griffin and Paul Singer, according to USA Today.

Meanwhile, though, another side of Wall Street is working to support Clinton.

Our campaign finance reporters estimated that Clinton and the PACs supporting her had received more than $21 million from Wall Street donors -- and more than that in total for her other campaigns in 2000, 2006 and 2008.

When she isn't debating, Clinton's relationship with Wall Street is friendlier. She had fundraiser at an investment firm in Philadelphia shortly before the Iowa caucuses at which Jon Bon Jovi was slated to appear. Two other fundraisers at finance firms scheduled before the New Hampshire primary have been pushed back until Democrats in that state vote.

During a previous debate, Clinton argued that she got more money from teachers and students than from Wall Street. She pointed people to the Center for Responsive Politics website -- and the organization obliged by raising questions about her claim. "Clinton is technically right," they wrote, "but there are some important caveats. Like super PACs." See above.

The bigger question, though, is this: Why some parts of Wall Street would work against Hillary Clinton. Another group, ESA Fund, ran this spot, targeting Sanders.

Or at least ostensibly targeting Sanders. In reality, the ad seemed as though it would bolster Sanders's chances against Clinton in a Democratic primary, since the fight in Iowa was being fought hardest over more liberal voters. (ESA Fund, the Huffington Post found, was funded in part by Singer and Griffin.)

Why would they want Sanders to win, given how hard Sanders rails against Wall Street? One big possibility is that they think Sanders is a weaker general election candidate. No matter who wins the Democratic primary, it seems likely that people on Wall Street will be much more likely to back the Republican.

Weakening Clinton so she loses to Sanders, they figure, gives them an easier target for November. (Voters agree that Clinton would be more likely to win than Sanders.) After all, if they're targeting her because they're afraid of her reforms, Sanders's vehemence on the issue should be giving them nightmares.

It's easy for Sanders to argue that Clinton has closer ties to Wall Street than he does; he has none. That's impossible for Clinton to avoid. This argument is perhaps her best bet to spin that negative into a positive. But the reason Wall Street wants Clinton to lose is likely because they want a Republican to win.

If the race came down to Sanders versus Clinton for the presidency, the situation would no doubt be very different.