By Michael Barone

New Hampshires first-in-the-nation presidential primary has featured contests between candidates for 60 years more than any other state in the nation. So this state with four-tenths of 1 percent of the nations population has played a key role in American politics.
New Hampshires votes for Democratic challengers Estes Kefauver in 1952 and Eugene McCarthy in 1968 prompted Presidents Harry Truman and Lyndon Johnson to announce they were not running for re-election days later.
And New Hampshires support in 1952 for Dwight Eisenhower then in Paris as a military commander over Mr. Republican Robert Taft launched Ikes successful candidacy. In 1964 a successful write-in effort for Henry Cabot Lodge then ambassador in Vietnam undermined his fellow liberal Republican Nelson Rockefeller.
Lodge enjoyed what seems to be a considerable advantage in New Hampshire: He was from neighboring Massachusetts. Other Massachusetts winners include Democrats John Kennedy in 1960 Michael Dukakis in 1988 Paul Tsongas in 1992 and John Kerry in 2004. Mitt Romney hopes to add another Republican name to the list this year.
If New Hampshire voters like Bay Staters they have been skittish about backing Southerners. Lyndon Johnson won only narrowly as incumbent president in 1968 and the lowest winning percentages in any contested race have been scored by Jimmy Carter of Georgia in 1976 and Pat Buchanan of Virginia in 1996.
The big exception to this rule was George H.W. Bush of Texas who was born in Massachusetts and grew up in Connecticut. He lost New Hampshire to Ronald Reagan in 1980 but won it in 1988 and 1992.
Sometimes it is not enough to win in New Hampshire; a candidate must beat expectations. In the 1972 Democratic race Edmund Muskies state director Maria Carrier said anything less than 50 percent for the Maine senator would be a loss. Muskie won 46 percent and George McGoverns 37 percent which placed him second put him on his way to the partys nomination.
Similarly in 1992 Bill Clintons poll numbers plunged during the Gennifer Flowers controversy. But on election night he came out and proclaimed that his 25 percent share of the vote which put him in second place made him the comeback kid. Paul Tsongas the winner with 33 percent hesitated to proclaim victory and Clinton won the nomination.
New Hampshire does not always vote for the eventual nominee. John McCain a big winner there in 2000 lost the nomination to George W. Bush.
In 2008 Hillary Clinton narrowly led Barack Obama there as she did in all primaries; he prevailed by winning big in caucuses and among superdelegates.
Among Republicans McCain beat Romney there 37 percent to 32 percent a margin almost identical to that by which McCain led Romney in 18 later primaries.