The major parties use a somewhat bemusing array of electoral mechanisms to choose their presidential candidates: winner-take-all primaries, caucuses, “open primaries” (any voter can vote in any party primary), “closed primaries” (only registered party members can vote), and “superdelegates.” So what, some folks ask, does the Constitution have to say about all this?
Not much. The men who wrote the Constitution generally had contempt for partisan politics, which they tended to view as necessarily narrow-minded and often corrupt. They were not blind to the possibility of political parties. The British political system had broken into Whigs and Tories for decades by the time of the Constitutional Convention. But the Framers made no provision for political parties, or for their regulation, in the Constitution. That omission seems partly to have flowed from a reluctance to do anything that might encourage the development of parties.
Their lack of attention to political parties also can be explained on less theoretical grounds. Though the Framers certainly experienced factionalism in their state politics — New York’s political life was almost tribal in its division among the Livingston, Schuyler, and Clinton clans — but there were no nationwide political parties yet in 1787. At the national level, sectionalism (New England versus the Middle States versus the South versus the West) was a much more potent force in the 1780s.
And it’s useful to remember that the Convention took seventeen weeks to hammer out the system we have; taking on additional subjects like political parties might have prolonged the thing beyond endurance.
On this point, as on quite a few others, the Framers left a lot of freedom to their descendants to shape American political culture. Most party structures — how to organize presidential primaries and choose delegates — are conducted by the state party organizations within a structure of state law. Thus, some states provide for caucuses, some for open primaries, some for conventions, some for closed primaries.
The national parties can set certain rules — such as the Democrats’ “superdelegates” — but national control is limited. To punish Florida and Michigan for putting their primaries too early in the year, the national Democratic Party has said it will refuse to seat some or all of their delegations at the National Convention in Denver. Yet Florida and Michigan went right ahead and had their primaries early.

Democratic Party Chair Howard Dean, in a difficult time
In early years of the Republic, presidential candidates were chosen in a caucus of a party’s congressmen and senators. The parties developed the national convention system, then our current program of caucuses and primaries. The system doubtless will continue to change.
McCain’s OK!
I wrote recently about whether John McCain is eligible to be president even though he was born in the Panama Canal Zone.
Although the legal/constitutional issue is an interesting one, the Obama and Clinton campaigns have announced that, so far as they are concerned, McCain is constitutionally eligible to be president. Which was what I concluded. Nice to see campaigns take sensible positions.