State Sens. Bob Worsley, Adam Driggs and Steve Pierce sent their letter urging a veto just days after they joined the entire 17-member Senate GOP caucus in voting for the bill.
"I think laws are (already) on the books that we need, and have now seen the ramifications of my vote," Worsley told The Associated Press. "I feel very bad, and it was a mistake."
With the three GOP senators joining all 13 Senate Democrats in opposition, there would be enough votes to defeat the measure in a re-vote. But too much time has passed to allow for reconsideration, and the bill was sent to Brewer in a routine transmittal Monday that was accompanied by "boos" from Senate Democrats.
Brewer now has five working days to sign or veto the bill. She returns from governors association meetings in Washington on Tuesday afternoon.
The governor doesn't comment on pending legislation, but she vetoed a similar measure last year. That action, however, came during an unrelated political standoff, and it's unclear whether she would support or reject this plan.
An estimated 350 people gathered outside the Arizona Capitol on Monday evening in a peaceful protest. They listened to speeches and many held homemade signs in opposition to the bill.
The bill is being pushed by the Center for Arizona Policy, a social conservative group that opposes abortion and gay marriage. The group says the proposal is needed to protect against increasingly activist federal courts and simply clarifies existing state law.
CAP President Cathi Herrod is urging Brewer to sign the legislation and deriding what she called "fear-mongering" from its opponents.
"The attacks on SB 1062 ... represent precisely why so many people are sick of the modern political debate," Herrod wrote in a weekend posting on the group's website. "Instead of having an honest discussion about the true meaning of religious liberty, opponents of the bill have hijacked this discussion through lies, personal attacks, and irresponsible reporting.
"Our elected leaders have a fundamental duty to protect the religious freedom of every Arizonan, and that's what SB 1062 is all about."
If SB1062 is vetoed, it will be a major defeat for Herrod's group, which is seen as a powerful force on the Arizona political scene. Herrod suffered a similar loss last year when she tried to get the Legislature to include anti-abortion language in a Medicaid expansion bill that Brewer was pushing. That effort angered Brewer, herself a strong opponent of abortion.
With the business community lining up against the latest proposal, Brewer could have cover for a veto. She's worked hard to return Arizona's economy to pre-recession levels with business-friendly incentives and tax cuts.
Apple spokeswoman Kristin Hueget confirmed Monday that the company had reached out to Brewer and urged a veto. Apple announced in November that it would open a manufacturing plant in the Phoenix suburb of Mesa that would employ up to 700 workers.
American Airlines CEO Doug Parker also urged Brewer to veto SB1062, in part to prevent damage to the state's economy, which is finally rebounding from the Great Recession. Parker ran Arizona-based US Airways until it merged with Texas-based American last year.
"There is genuine concern throughout the business community that this bill, if signed into law, would jeopardize all that has been accomplished so far," Parker wrote. "Wholly apart from the stated intent of this legislation, the reality is that it has the very real potential of slowing down the momentum we have achieved by reducing the desire of businesses to locate in Arizona and depressing the travel and tourism component of the economy if both convention traffic and individual tourists decide to go elsewhere."
Pierce said he and the others went along to present a solid Republican front, despite misgivings.
"We were uncomfortable with it to start with and went along with it thinking it was good for the caucus," Pierce said. "We really didn't want to vote for it, but we made a mistake and now we're trying to do what's right and correct it."
But their letter also said while the intent of their vote "was to create a shield for all citizens' religious liberties, the bill has been mischaracterized by its opponents as a sword for religious intolerance."
The bill allows any business, church or person to cite the law as a defense in any action brought by the government or individual claiming discrimination.
Opponents call it a license to discriminate against gays.
Similar religious protection legislation has been introduced in Ohio, Mississippi, Idaho, South Dakota, Tennessee and Oklahoma, but Arizona's plan is the only one that has passed. The efforts are stalled in Idaho, Ohio and Kansas.
Republicans stressed that the bill is not about discrimination but protecting religious freedom. They frequently cite the case of a New Mexico photographer who was sued after refusing to take wedding pictures of a gay couple. They said Arizona needs a law to protect people in the state from heavy-handed actions by courts.
Another frequently cited example is a suit brought against an Oregon baker who refused to make a wedding cake for a gay couple.
The businesses were sued, but those efforts came under state laws that extended protected-class status to gays. Arizona has no such law protecting people based on sexual orientation.
Follow Bob Christie at http://twitter.com/APChristie.