Congestion taxes are the latest in a long line of magic bullets proposed to solve all city problems. One of the clear differences between congestion taxes and other oft-cited magic bullets (stadiums, convention centers, starchitectural public monuments, casinos, etc), is that there are actually clear, demonstrable examples of success around the world, particularly in London and several Swedish cities such as Gothenburg and Stockholm:
The theory is that the vehicles entering the core are effectively taking up space, polluting, degrading the public environment, and through their presence are stultifying the internal combustive socio-economic activity that defines cities, so they must pay to offset that cost they impose. It is quite logical provided the context is appropriate.
New York City has already shown the challenge politically in implementing a congestion tax even though in all probability would've been extremely beneficial in NYC. However, when I read or hear people suggest congestion taxes without offering the context of when and where, let alone in Sun Belt cities, I feel compelled to point out how catastrophic they would be in the Sun Belt. What we have to understand is that whatever cities are doing elsewhere, often don't apply here. Sun Belt cities, though governed by similar forces, have become entirely different organisms than cities of most of the rest of the world.
Congestion taxes have worked where they have (and would've worked in NYC) because demand is still high in the core and would be high enough to sustain a given rate just to enter the core in a private vehicle. In the sun belt, where the core is hollowed out by the infrastructural system, there isn't a similar demand. If implemented in a place like Dallas, it would only halt any shifts back towards the core and reverse the inward movement of the real estate market. People would effectively say, "why would I need to ever go down there again?"
As a basic formula, if you want to know whether a congestion tax is appropriate in a city, just compare the cost of parking (here's a telling overview), ie, are businesses or customers shrieking, "OMG we can't lose our free parking!!!!111!!! ?" It's very expensive in the places where congestion taxes have worked successfully because space is at a premium. Not so coincidentally again, the congestion tax decreases demand for parking thus dropping parking costs to the point where the space for parking can be repurposed to something more invaluable.
In effect, a congestion tax in the sun belt would have the opposite effect of what is intended, to improve the real estate market in the core, maximize livability, and land use efficiency. Instead, it would be the final nail in the coffin. Rather than pursuing more inappropriate "cut-n-paste" urbanism, the answer to shifting the real estate market back towards the downtown core is in the highways, more specifically the land occupied by them.