John F. Kerry went to Colorado on Friday -- a state that a Democrat has not won in more than a decade. It was his fourth trip there since June. President Bush campaigned in the state earlier in the week.

Why all the attention? On the Nov. 2 ballot is a voter-driven initiative to amend Colorado's constitution and make it the first state in the nation to award electoral votes based on the percentage of the popular vote each candidate wins, effective this election. That could have a profound impact on who is elected president.

It means that Kerry could lose the state but still win four of its nine electoral votes, according to Democratic backers and Republican opponents. That prospect has prompted the GOP to mount a fierce challenge to the initiative even as they prepare for a possible post-Election Day legal showdown.

"If numerically it makes a difference, there certainly could be a legal challenge . . . whether from a candidate or the people of Colorado," said George J. Terwilliger III, who was a senior member of Bush's legal team during the 2000 Florida election recount. "This has the potential to cast a cloud over a close election."

Rick Ridder, the campaign manager for the "Make Your Vote Count" initiative, said that the disputed 2000 election in part prompted the ballot drive. Then, Vice President Al Gore won the popular vote nationally but fell five votes short in the electoral college. "This is an affirmation of the basic principal of one person, one vote," Ridder said. "It makes every vote count, and it gives greater weight to the individual."

The founders devised the electoral college as part of a federalist sharing of power between the states and the national government. Each state gets one electoral vote for each of its U.S. House representatives, and one electoral vote for each of its two U.S. senators. All but two states award their electoral votes on a winner-take-all basis; Maine and Nebraska allot two votes to the statewide winner and the rest to the winner in each congressional district.

Opponents of the measure such as Colorado Gov. Bill Owens (R) argue that the initiative would diminish Colorado's power on the national stage. Presidential candidates will care less about the state if it offers a chance to pick up one electoral vote instead of the current bonanza of nine, Owens reasons.

"I think that impacts future decisions on things like potential [military] base closings or federal highway funding allocations," said Owens spokesman Dan Hopkins.

The initiative was placed on the ballot through a voter petition. Hopkins said the most recent private polls he saw showed that the initiative had majority support, but he added that was the situation before Owens and others began campaigning against it.

If the measure succeeds in November and the presidential election hinges on the allocation of Colorado's electoral votes, opponents are vowing a constitutional battle that could leave the outcome in doubt after Election Day. Terwilliger said that the legal questions over the Colorado initiative present many of the same core issues that were at the heart of the 2000 Bush v. Gore fight. The U.S. Constitution gives each state the power to appoint electors "in such manner as the legislature thereof may direct." Terwilliger noted: "The power over how electors are chosen is reposed in the legislature, not in the people, and yet here you are having the people decide. I think there's a real question here as to whether the federal courts would not invalidate the results of the initiative."

Proponents cite recent Colorado Supreme Court and U.S. Supreme Court decisions that found that the people have the right to draw new legislative districts, even though the Constitution specifically gives that power to the state legislature, because the legislature ceded part of its authority to the people by allowing direct voter initiatives.

"Our argument is that under Colorado law, the people are the greater legislature," said lawyer Mark Grueskin, who drafted the Make Your Vote Count initiative.

It is possible that the vote on the initiative could be close enough to require a recount, a scenario that could prompt the GOP-controlled Colorado legislature to step in and decide the election. But House Speaker Lola Spradley (R) said that is unlikely to happen. "While we might sue to see if there were flaws," she said, "if it was upheld, we would feel some obligation to go with what the people voted for, even if we hated it."

President Bush campaigns with NFL Hall of Famer and former Denver Broncos quarterback John Elway, left, and Colorado Gov. Bill Owens (R) in Greenwood Village, Colo.