At some of the race blogs I read, now and then someone comes along and makes a comment about how frequently people with last names ending in A have done something. It's usually said in a sort of way that suggests names ending in A are a good representation of underrepresented groups. With Barack Obama winning the Iowa caucuses, the possibility of a President Obama all of a sudden seemed a lot more viable, and sure enough a comment appeared in the comments here wondering who the highest-ranked person with a last named ending in A might have been.
Even if there are much more precise, and probably more accurate, ways of measuring underrepresented people in government positions, I thought it was an interesting question, so I investigated it. It turns out there aren't that many in the highest positions. One problem, though, is how you measure rank. There is an official measurement of ceremonial rank for matters of state, but there's nothing to that but ceremony. Laura Bush is higher rank in terms of ceremony than Dick Cheney, but she has no official authority in reality. The mayor of a small city outranks the Chief Justice of the United States when in that city, according to this list, and that's surely not a good way to measure rank in the way this commenter meant.
The other problem is that there are three branches of equal rank, and it's hard to compare whether someone of significant authority in one should be over someone of significant authority in another. How do we compare the rank of the president with the rank of the Chief Justice? How do we compare the rank of the Majority Leader of the Senate with the rank of Associate Justices of the Supreme Court? So any answer to the question is going to be a bit messier than the question might at first make it sound, but there are some interesting answers to give.
In the executive branch, you can provide some order. The president, v.p. and then cabinet do seem to have a ranked order (because of the order of succession, although that doesn't really reflect influence: is Homeland Security less influential than Veterans' Affairs?). It turns out the highest rank in the executive branch for someone with a last name ending in A is Attorney General. That person was Joseph McKenna under President McKinley, who later became a Supreme Court Justice. But then I don't know how to rank chiefs of staff, and I think they might have more influence than some cabinet members even if they don't seem as prominent in any official constitutional capacity. Leon Panetta and John Podesta have been chiefs of staff. They do appear in the ceremonial ranking under cabinet secretaries, though.
In the judiciary branch, it's obvious that Chief Justice of the U.S. is the highest position and then the associate justices. McKenna again was the first justice with a last name ending with A, and of course now we've got Antonin Scalia. If you move down a level to appeals court judges, we've had Abner Mikva and Antonin Scalia on the D.C. Circuit. Juan Toruella and Bruce Selya are both current members of the First Circuit. Harold Medina was on the Second Circuit. Emilio Garza is on the Fifth Circuit. The Ninth Circuit has Carlos Bea, Sandra Ikuta, and Wallace Tashima. It previously had the aforementioned Joseph McKenna The Tenth Circuit has Deanell Tacha. The Eleventh Circuit has Joel Dubina. The Federal Circuit has Arthur Gajarsa. I didn't notice any on the Third, Fourth, Sixth, Seventh, or Eighth Circuits.
The legislative branch is harder. The two constitutional roles in the line of succession (Speaker of the House, President Pro Tempore) haven't had anyone with names ending in A. There haven't been any Majority or Minority Leaders, or Majority or Minority Whips ending in A. The only other higher-ranked positions I can think of are committee chairs. I doubt Barack Obama has chaired any major committee (although he may chair a subcommittee), but Daniel Akaka has. Joseph Montoya and Akaka's predecessor, Spark Matsunaga, also held no committee chairships as far as I can tell. In the House, 14 current members have last names ending in A. I'm not going to look through all the former members there or try to figure out who has held committee chairs, but several of them are pretty senior, and at least two are currently ranking members on important committees.
Then it's hard to know how to compare state level to federal level. I didn't look at all the states for governors, but New Mexico was an obvious one to look at, and they've had three, one as far back as a century ago (around Joseph McKenna's time).
Ambassadors might also count as pretty high-ranking. Currently, Cesar Cabrera is ambassador to Seychelles. I don't know of an easy way to look for others without a lot of time-consuming clicking in Wikipedia, but there is at least this one.
If you do go by the ceremonial order of precedence, the highest-ranked among these would be the governors (only in their state) and then ambassadors (while at their posts). If you're not in a state with a governor with a name ending in A (and Spitzer certainly doesn't) and aren't at the post of an ambassador whose last name ends in A (and I'm not in the post of any U.S. ambassador), then the highest-ranking official with a name ending in A is currently none other than Justice Antonin Scalia, by this ceremonial measure. So by that measure, the answer to the question is ironically someone the person asking the question likely despises.
Update: I found some more governors and ambassadors:
Rudolf Perina (ambassador to Armenia)
Sharon E. Villarosa (ambassador to Burma)
Cesar Cabrera (ambassador to Mauritius)
Antonio O. Garza Jr. (ambassador to Mexico)
Preston Lea (governor of DE, 1905-1909)
William Paca (governor of MD, 1782-1785)
Jonas Galusha (governor of VT, 1809-1813)
Joseph Desha (governor of KY, 1824-1828)
Henry L. Fuqua (governor of LA, 1924-1926)
John W. Dana (governor of ME, 1844, 1847-1850)
L. B. Hanna (governor of ND, 1913-1917)
Ezequiel C. de Baca (governor of NM, 1917)
Jerry Apodaca (governor of NM, 1975-1979)
Toney Anaya (governor of NM, 1983-1987)