If Hillary is the Democrat nominee, who might her VP be? Does it really matter?

[pbrower2a]

VP doesn't matter that much unless the VP (to the political positive) fends off a possible rift or (to the negative)

(1) has no experience in high public office (US Senate, state governor strongly preferred. Does "mayor of a large city" count?) Congressional representatives do badly as political assets (William Miller, Geraldine Ferraro, Jack Kemp, Paul Ryan)

(2) has a problem -- see Thomas Eagleton, 1972.

(3) is grossly unqualified  -- Sarah Palin.

(4) is an incompetent campaigner

The VP nominee rarely swings a state. Ideological consistency has far greater significance. Bill Clinton could have chosen some Northern pol as his running  mate in 1992, but he selected a Senator from a neighboring state (Tennessee) with demographics and political heritage similar to that of Arkansas. He still won a raft of states that no Democratic nominee had won after the LBJ blowout of 1964.  

Here I discuss Julian Castro because he would bring an unusual experience and new political characteristics to national politics:

If Hillary Clinton selects some Democratic Rep from Florida just to win Florida -- such will either be irrelevant or fail. Selecting a big-city mayor (Julian Castro) would be daring because it just has not been done. The strengths of a big-city mayor (San Antonio) are obvious -- top official of a populous entity. Mayors have administrative experience that legislators do not have. Mayors must deal with local issues.

He would be the first Hispanic nominee of any major Party, and even if he does not swing Texas he might help in Colorado and Nevada  by encouraging the large Mexican-American populations in both states to vote. Who knows -- he could conceivably swing Arizona, a state with some affinities to Texas. The GOP nominee really must win at least one of Colorado and Nevada to get elected President. Such could solidify the Obama coalition, and the Obama coalition is enough for winning the Presidency.

The negatives? First, the city is San Antonio, a city with big problems. It's a nice place to visit but statistically an awful place in which to live. San Antonio has below-average economic conditions, poor statistical measures of educational achievement, and a high crime rate. Count on Republicans using that against him. (Democrats would have probably used that against former Cleveland Mayor, Governor of Ohio, and Senator Voinovich -- who I concede might have been a fine President had he been elected). Just about any big city has much the same problems.

Second, San Antonio is no microcosm of America. Like most other giant cities in Texas it has incorporated land that might have formed suburbs, so it has some sections with suburban qualities.  But it is not at all rural. Its ethnic mix is uncharacteristic of America. What works in San Antonio might not be so attractive in Wisconsin.  Julian Castro has never shown any ability to appeal to rural voters. Rural voters did not decide elections of 2006, 2008, or 2012, but they did decide the election of 2010.

Third -- the surname. It will be terribly unpopular in Florida even if he is no relation to someone  infamous to many Floridians.  If he must spend much time distinguishing himself from Fidel, then the adage "if you are explaining you are losing" applies.