Presidential elections now fought over a small number of voters

If there is a theme to this year's U.S. presidential election, it is Barack Obama's small but consistent lead over Mitt Romney.  It really is a sign of the current polarization of politics in America, where parties fight over a small number of undecided voters.  It is a trend that has its roots in the divisive politics of the Gingrich lead Republicans in the 90s and accelerated with the election of George W. Bush in 2000.  Even Obama's "landslide" win in 2008 was smaller than landslides of past eras and only made possible by the unprecedented unpopularity of Bush and a weak Republican candidate in John McCain.  Obama won in 2008 with 53% of the vote compared to John McCain's 46% of the vote and with 365 electoral votes compared to 173.  Compare that with Ronald Reagan's 1984 win over Walter Mondale in which Reagan carried every state but Minnesota and the District of Columbia, or Richard Nixon's 1972 win over George McGovern in which Nixon won the popular vote by a 61% to 38% margin and again won every state save for Massachusetts and DC.  Today over half the states are automatic wins for one party or another.  The chart below illustrates this trend more clearly.  Democrat winners are in blue and Republican winners are in red.  (I apologize for my poor Blogger skills, they don't make it easy to make tables)

Year    Dem. candidate     Rep. candidate     popular vote    electoral vote    states won
1964    Johnson               Goldwater                   61 - 39               486 -  52              44 -  6
1968*  Humphrey            Nixon                         43 - 43               301 - 191             32 - 13
1972    McGovern             Nixon                        61 - 38               520 -    17             49 -  1
1976    Carter                   Ford                             50 - 48               297 - 240             23 - 27
1980    Carter                     Reagan                      51 - 41               489 -   49             44 -   6
1984    Mondale                 Reagan                      59 - 41               525 -   13             49 -   1
1988    Dukakis                  GHW Bush             53 - 46              426 - 111              40 - 10
1992    Clinton                GHW Bush               43 - 38               370 - 168              32 - 18
1996    Clinton                Dole                             49 - 41               379 - 159              31 - 19
2000    Gore                        GW Bush                48 - 48               271 - 266              30 - 20
2004    Kerry                      GW Bush                51 - 48               286 - 251              31 - 19
2008    Obama                  McCain                      53 - 46               365 - 173              28 - 22

(* in 1968 American Independent candidate George Wallace captured 5 states and 46 electoral votes with 14% of the popular vote)

The trend is quite obvious, the popular vote has become increasingly close, on average, while at the same time as like minded people become more and more concentrated in the same places, the number of safe states have increased for both parties (although the increase in states now out of play have been more pronounced for the Democrats).  As the number of voters that can be influenced continues to dwindle, elections will continue to be fought in a handful of states where the two parties are more or less evenly matched.