Suddenly, smaller and much more conservative states would have as much of a voice at the convention as some of the larger swing states where general elections are usually won or lost.

“In a typical year, it doesn’t matter,” said William G. Mayer, a professor of political science at Northeastern University who has written on the nominating process. “This year it may matter again.”

To understand how the Republican Party allocates delegates to states, consider Mississippi, which gets 40. Fifteen of them are “bonus delegates,” the party noted — nine to reward the state’s heavy Republican vote in the 2008 presidential election, one for having a Republican governor, one for each of the state’s two Republican senators, one for electing a majority of Republicans to the state’s House delegation, and two for controlling both chambers of the Legislature.

Democrats use a different formula, but with the same result — theirs takes into account the sum of the state’s vote for Democratic candidates in the last three presidential elections. Democrats also make many Democratic elected officials into unpledged “superdelegates,” which also has the effect of amplifying the power of the states that elect the most Democrats.

The practice of giving extra weight to the most partisan states has its roots in the bitter Republican Party divisions of a century ago, said Barbara Norrander, a professor at the University of Arizona who wrote “The Imperfect Primary: Oddities, Biases and Strengths of U.S. Presidential Nominating Politics.”

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After William Howard Taft won the 1912 Republican nomination over Theodore Roosevelt — in part because of the support he got from delegates from the South, which was then heavily Democratic — some Republicans questioned the wisdom of giving a Democratic region so much sway when it comes to deciding whom the Republicans should nominate, Professor Norrander said. Four years later, she said, the Republican Party devised a system that took delegates away from Southern states, and not long after that the party moved to adopt a system of awarding bonus delegates.

Members of both parties said that it made sense to give more sway to party loyalists.

“The theory behind it is plain enough: to reward success,” said David A. Norcross, the former chairman of the rules committee of the Republican National Committee.

Mr. Norcross noted that as parties have turned to primaries and caucuses in recent decades, the importance of conventions and delegate counts has waned, lessening the impact of bonus delegates. Most candidates now win the nomination by winning enough of the early contests to drive their competitors from the field. “Momentum usually takes the place of delegate counts,” he said.

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“If you got down to the point where you’re counting, like we were in ‘76, then it would matter,” he said, referring to the 1976 Republican National Convention, when President Gerald R. Ford and Ronald Reagan arrived without the number of votes needed for the nomination, but Mr. Ford swayed enough delegates to win narrowly on the first ballot. “My prediction is we’re never going to get there.”

Elaine C. Kamarck, a lecturer at the John F. Kennedy School of Government at Harvard who has been on the Democratic National Committee’s rules and bylaws committee and has served as a superdelegate, said that while the extra weight given to the most partisan states has had little impact in past elections, it could play a role in a tight race.

“Once you are in a delegate race, once you don’t have an early knockout, then everything matters,” said Ms. Kamarck, the author of “Primary Politics: How Presidential Candidates Have Shaped the Modern Nominating System.” “The allocation of delegates matters, the distribution of the delegates across the states matter, who’s going to win more Congressional districts matters.”

Many states clearly believe that voting early — in the hopes of bestowing that hard-to-quantify “momentum” — is more important than getting more delegates. This year New Hampshire, Arizona, Florida, Michigan and South Carolina all bucked the wishes of the Republican Party and held their contests early — despite the party’s vow to penalize them by cutting half of their delegates. That could have a much greater impact than the bonus delegates, if the race is close: those penalties could particularly hurt Mitt Romney, who won all of those states but South Carolina, which Newt Gingrich won.

In the meantime, the Republican Party’s tendency to reward loyal states — and give all states 10 delegates regardless of population, which increases the clout of small states — gives many small states more influence in the nominating process than they will have in the general election. Georgia, which Mr. Gingrich won, is smaller than Ohio, but it gets more delegates thanks to the bonus delegate system. Nevada is nearly four times as populous as North Dakota, but both states get the same number of delegates. The Democratic primary calendar has its own anomalies.

“It points to the weirdness of the way in which we nominate our presidents,” said Thomas E. Mann, a scholar at the Brookings Institution.