Now that Ray LaHood has finally announced he is stepping down as President Obama's Secretary of Transportation, speculation has immediately focused on whether outgoing L.A. Mayor Antonio Villaraigosa will succeed him.

There's no question that Obama needs a Latino in the Cabinet. It's not clear whether Obama thinks he needs a big name like Villaraigosa at DOT, and Villaraigosa claims to have taken himself out of the running because he doesn't want to leave office before his term is over on June 30.

But that, in and of itself, doesn't necessarily mean he's out.The timing and messaging of LaHood's departure would seem to point in Villaraigosa direction: LaHood took his time making a decision and made it clear he'll stay on until a successor arrives.

But maybe the most interesting question raised by the Villaraigosa possibility is whether a mayor is the best choice the DOT job. As  a recent blog in Atlantic Cities noted, there's a pretty good case for a  mayor as opposed to a career transportation expert or a transplant from Capitol Hill. 

The job is important to planning and development because the Department of Transportation has by far the most money of any federal agency involved in the field. It's one of three agencies (Environmental Protection Agency and Housing and Urban Development being the other two) involved in the Obama's Partnership for Sustainable Communities. And, of course, transportation investments drive development patterns.

Villaraigosa's name is in play because he is a high-profile Latino with a strong record of accomplishment in the transportation field. On his watch, L.A. has moved to the forefront on rail transit construction, and Villaraigosa has eloquently advocated for "elegant density" as a solution to the city's problems.

Most recent Transportation Secretaries have been either transportation professionals (like Mary Peters in the Bush Administration) or members of Congress who worked on transportation issues (like Norm Mineta, who had also been a mayor, and Ray LaHood). In the case of both Mineta, a Democrat, and LaHood, a Republican, the incumbent president used the DOT slot to give a Cabinet job to a respected member of Congress from the other party.

But, as Atlantic Cities points out, mayors have a different take on DOT than other folks, because they view transportation as part of the overall system of their city's functions and they are more likely to view transportation investments in economic development terms.

In many ways, Villaraigosa resembles former Denver Mayor Federico Pena, who was President Clinton's first DOT secretary in 1993. Pena was a well-respected Latino mayor who had gotten one big transportation project done (the new Denver Airport) and had laid the groundwork for urban redevelopment both downtown and at the old Stapleton Airport site. (You can read a piece I wrote about Pena at the time here.) Pena did not have nearly the high national profile that Villaraigosa has, however.

Pena sometimes seemed over his head in the job at first, but in the end did a good job. But it was easier to be Secretary of Transportation in those days, principally because of money and politics. The pathbreaking ISTEA law had passed with bipartisan support just two years earlier and the federal gas tax had gone up. Now, the federal Highway Trust Fund is bankrupt and it took Congress four years to pass an 18-month extension to the transportation bill. It is also hard to know how Villaraigosa -- a big city mayor -- would handle the state DOTs, who have enormous influence over how transportation money is spend. It is worth noting, however, that he spent six years in California Assembly, rising to the position of Speaker.

In the end, the question of whether Villaraigosa goes to DOT is a political calculation on both sides -- whether President Obama sees an advantage to having this high-profile Latino in his Cabinet, and whether Villaraigoisa views the DOT job as a useful stepping stone toward his presumed next goal, a run for governor after Jerry Brown steps down. But it would be interesting to see whether Villaraigosa can push a smart growth transportation agenda more effectively than anybody else.