You often hear that Bachmann was born in Iowa and lives in Minnesota, so that will help her in Iowa. Or that Romney is from Massachusetts so he'll do well in New Hampshire.
In 1976, Gerald Ford (R, MI) lost Ohio and the election. Michigan and Ohio share obvious similarities of economics. In 1993 Bill Clinton lost Mississippi, Oklahoma, and Texas both times. In 2000 Al Gore lost not only Tennessee but also all eight states bordering Tennessee. In 2008 John McCain lost three of the four states that border Arizona, and Barack Obama lost Missouri and Kentucky.
If the neighboring state is very different from the one from which the candidate is from in political culture (Barack Obama is a very poor match for Kentucky but excellent for Illinois) then one can usually expect a loss in the very different state in a general election.
The Favorite Son (usually worth about 10%) effect ends at the state line. If the nominee is extremely strong in his own state, then he can expect most bordering states to follow. But if you are looking at Indiana, it may be more significant that the headquarters for the campaign of President Obama was located in Chicago and that very soon the paid staff there had little electioneering to do in Illinois... or some neighboring or near-neighboring states (Wisconsin, Iowa, Michigan), so if such staff had some spare time they might work Indiana.
Mitt Romney has never been politically active in New Hampshire as an elected official. New Hampshire, far more R-leaning than any Northeastern state except West Virginia and Indiana, is more likely than its neighbors to vote for Romney in the general election because it is more Republican. New Hampshire is the only state north and east of the Potomac to have voted for any Republican for President after 1988, and if Mitt Romney should win even some of the near-neighbors (Connecticut, New Jersey, New York, or Rhode Island) then he has surely won a landslide. The same would be true in reverse if President Obama were to win Kentucky, Tennessee, or Arkansas.
Gingrich fails in the South because he is a
faux intellectual; Perry is a blatant anti-intellectual who appeals to the anti-intellectual attitudes of white Southerners. President Obama is a real intellectual, so a matchup between Gingrich and Obama would be interesting in the South, where white people with strong local ties would see themselves with a choice between two objectionable characters.
Bachmann seemed likely to win over the Republican vote in Iowa for the primaries for a while because Iowa Republicans are as religious and reactionary as Republicans almost anywhere.
Someone had a chart of how the states voted in Presidential elections based on how states voted together. At the extreme, Alabama and Mississippi haven't voted differently (although the Civil War and Reconstruction did prevent some votes) since
1840. Hawaii and Rhode Island have voted together since 1960, and it is hard to think of states more separate in geography than those two... except perhaps Alaska and Oklahoma.
Thirteen states (except for the bare one-time exception of the Second Congressional District of Nebraska) have voted for the Republican nominee for President, and seventeen states and DC have voted for the Democratic nominee for President in the last five Presidential elections. Nobody would confuse South Carolina and South Dakota, and nobody would confuse Pennsylvania and California.
