Image Credit: David Goldman/AP Photo

ABC News' Michael Falcone and Chris Good report:

TAMPA - Tampa may have avoided the worst of the soon-to-be hurricane, but a storm of a different kind is brewing at the Republican National Convention.

Members of the Republicans' National Committee from across the country may be on the verge of a messy fight over party rules on the very same day they are poised to crown Mitt Romney as their presidential nominee.

At issue is whether presidential candidates can effectively pick and choose the delegates who attend the convention. Opponents of a new party rule have called it "the biggest power grab in the history of the Republican Party" while supporters are hoping to avoid a public dispute on the convention floor during a week meant to promote unity.

Last week, the RNC Rules Committee approved a controversial change to the delegate selection process. Currently, states hold primaries and caucuses to determine how many delegates will be awarded to each candidate, but state parties generally meet later at state conventions to actually choose those individuals.

The new rule, however, gives presidential candidates veto power over their own delegates, representing a big boost in power for the candidates and a reduction for states. If Mitt Romney, for instance, didn't like a delegate slated to cast a vote in his favor at the convention, Romney could throw him out and choose an alternate.

"This is the biggest power grab in the history of the Republican Party because it shifts the power to select delegates from the state party to the candidate," Republican National Committeeman Jim Bopp of Indiana said in an e-mail message to fellow committee members obtained by ABC News. "And it would make the Republican Party a top-down, not bottom-up party."

Bopp, who is one of the leaders of a movement to squash the changes, called the proposal an "overreaction to the problems in a few states where Ron Paul delegates threaten to not support the winning presidential candidate."

RNC members like Bopp who are discontent with the move have proposed their own measure to block it - what they refer to as a "minority report," which would remove the new rule.

Supporters of the change, including Romney loyalist Henry Barbour, a national committeeman from Mississippi and the nephew of the state's former governor, Haley Barbour, are lobbying members against proposing the "minority report" (and, thus, avoiding any potential drama in the convention hall on Tuesday).

"We believe a minority report is futile and will only encourage division on the floor," Barbour wrote in a private message to RNC members Sunday night. "Now is the time to unite behind Governor Romney."

One top Republican told ABC News that the simmering tensions represented a "serious revolt" by some RNC members against the Romney allies who proposed the changes and that any type of floor debate on Tuesday - when Romney and running mate Paul Ryan will officially be nominated as the presidential and vice presidential candidates of the party - would be "highly unusual."

And opponents showed no signs of backing down.

"I am shocked that this rule passed," Republican National Committeewoman Kim Lehman of Iowa wrote in an internal e-mail message. "Every delegate that I have shared this with is upset and stunned that something so undemocratic could come from the Republican Party. This new rule needs to be stopped. Not only is this a power grab, this is a change of governance from 'We the People' to the Candidate."

Republicans are also poised to make it harder for candidates like Ron Paul to amass delegates and influence over the convention.

In 2012, Paul's supporters focused heavily on caucus states where the Texas congressman could amass delegates without winning the statewide vote. His backers exploited their in-depth knowledge of state party rules in states where party conventions - not statewide presidential votes - determined how many delegates Paul would bring to the GOP convention in Tampa.

Under the new rule, that strategy would no longer be viable, and candidates like Paul would no longer be able to gather delegates in caucus states. Instead, statewide votes would bind delegates in every primary or caucus.

Paul managed to collect a plurality of delegates in four states. Had this rule applied in 2012, Paul would have collected a plurality in none.

"The rules change here is overkill," Bopp wrote in his message Sunday night, likening it to "killing a fly with a sledgehammer."

On a conference call with reporters on Monday, Romney campaign strategist Russ Schriefer played down the potential for "disunity."

"We are a big party. We have people with different, opposing viewpoints. I don't think this is a particularly divisive point of view on which people are divided on, but the one thing we know is we're all united in defeating Barack Obama," Schriefer said. "I guarantee you on Thursday, as we walk out of this convention, we will be one hundred percent united behind electing Mitt Romney and defeating Barack Obama for the good of the country."