Tonight’s primaries in Alabama and Mississippi certainly have implications for Mitt Romney in the long term, but they will be decisive for another powerful Republican: Alabama Representative Spencer Bachus, who is currently chairman of the House Financial Services Committee.

He is facing a strong primary challenge from state Senator Scott Beason, a virulent anti-immigrant grandstander and author of Alabama’s draconian H.B. 56, which caused thousands of Hispanics to flee the state. But Bachus is also being battered by ads from the Texas-based, anti-incumbent Campaign for Primary Accountability Super PAC—the same group credited with helping to oust Representatives Dennis Kucinich and Jean Schmidt in Ohio last week.

The Super PAC is pummeling Bachus for his massive Wall Street contributions—he’s received nearly half of his donations this cycle from the financial sector—and for an ongoing ethics investigation into whether Bachus profited from insider knowledge in the run-up to the financial crisis. (60 Minutes nailed Bachus on this late last year, in the same piece that led to the pending passage of the STOCK Act.) Advertisements like this one have been running in Alabama for weeks:

That ad hits Bachus for financial sector donations, but then it gets fuzzy by portraying a quid pro quo when Bachus voted for the financial sector bailout. The bailout is certainly unpopular in deeply conservative areas, but Bachus has done much more insidious tasks for Wall Street than supporting a basically necessary rescue plan.

As Pat Garofalo at ThinkProgress notes, in recent years Bachus sought to weaken the Dodd-Frank financial reforms, including gutting the Consumer Financial Protection Bureau; he’s sought to dramatically weaken the budget of financial regulators and has also sought to undermine foreclosure prevention programs. (He notoriously said before taking the chairmanship that the job of regulators is to “serve the banks.”)

Wall Street loves the guy, which is why Bachus has received funding for a final push in the past few days from Citigroup, Barclay’s and RBS, among others. He’s mounting a $1.5 million advertising counteroffensive portraying himself as a consistent opponent of the Obama administration and in particular the healthcare reform bill.

It’s going to be a nerve-wracking night for Bachus, with the race expected to be very close. Wall Street would lose a key ally in Bachus if he goes down, but let’s also be realistic—the next Republican in line on Financial Services will be lavished with the same donations, and will likely carry out the same agenda. Still, Bachus’s skill, experience and contacts will be missed by the Street.