Rudy Giuliani and John McCain, the leaders in Republican polls during most of the year, have announced they will not compete in the straw poll held in Iowa on Aug. 15. Fred Thompson, who is polling well and expected to enter the race, may also opt out of this early test of strength. Florida has moved its primary to Jan. 29, just one week after New Hampshire and shortly after the actual Iowa caucus, in defiance of Democratic Party rules. (Florida Democrats risk being tossed out of the national convention but say they don't care.) Michigan Democrats have also said they'll hold a caucus on Jan. 29, or even earlier if New Hampshire acts on its threat to move its primary back.

All these moves are threats to the rule that Iowa and New Hampshire vote first. In fact, the process was begun by the Democratic National Committee, which has authorized a Nevada caucus and a South Carolina primary just after the Iowa and New Hampshire contests. Now others are joining in the attacks.

And a good thing, too, is my gut reaction. I have thumbed through my copy of the Constitution many times to find the part that says Iowa and New Hampshire come first, and I have yet to find it. And in fact they have not always come first. Both have been around for about a century. But in their modern form, New Hampshire first listed candidates on its ballot in 1952, and Iowa held the first of its first-in-the-nation caucuses in 1972. Ever since, these two states have lobbied -- browbeaten, actually -- presidential candidates to pledge to maintain their monopoly. For more than a quarter century, the blackmail has worked. But it's not clear that it's going to work any more.

The case for Iowa and New Hampshire goes along these lines. They are small states with small electorates -- 250,000 caucusgoers in Iowa (out of a population of 3 million) and 450,000 primary voters in New Hampshire (out of a population of 1.3 million) -- who are used to evaluating candidates firsthand. They are thus venues for retail politics, which is impossible in large states.

The case against them is that they are scarcely typical of the nation (they're 93 percent and 95 percent white, for example) and may not produce the best national candidates. They are overly influenced by locally important issues. For instance, you don't want to run in Iowa if you've voted against ethanol subsidies. And woe to you in New Hampshire if you voted to shut down the Portsmouth Naval Shipyard. Iowa is unusually dovish, as are New Hampshire Democrats. New Hampshire Republicans are unusually averse to tax increases.

True, those states can be hard to ignore. Candidates running third in national polls -- Mitt Romney and John Edwards -- are leading in the Iowa polls, with Romney leading in New Hampshire, as well. A win is still a win, and both hope to get a bounce that will give them valuable momentum going into Nevada, South Carolina, Florida, Michigan and the many states scheduled to vote on Feb. 5. But the crowd of early contests also raises the possibility that voters in the big states may decide they don't need to take instruction from Iowa and New Hampshire. That's what Giuliani and McCain and maybe Hillary Clinton and Barack Obama are betting on.

If that turns out to be the case, we will have moved toward a de facto early national primary, which not only devalues retail politics but forces voters to make a decision all at once without seeing how candidates stand up under the rigors of campaigning.

Is there an alternative? My favorite is the Delaware Plan, which came close to being endorsed by the 2000 Republican National Convention. It has four rounds of primaries or caucuses, with the 12 smallest states voting in March, followed by the 13 next largest in April, the next 13 in May and ending with the final 12 largest states voting in June. This would leave plenty of room for retail politics, with candidates able to pick the states where they might run best. Voters in later states would be able to judge how candidates run the gauntlet.

The nominations could not be clinched until June, since the 12 largest states have 60 percent of the nation's population. The parties could endorse this system at their national conventions. Or if there was bipartisan support, Congress could impose it as federal law. Iowa and New Hampshire have been disproportionately powerful for 30-plus years now. But maybe not forever.