Texas Gov. Rick Perry speaks at the National Conference of State Legislatures Legislative Summit at the Henry B. Gonzalez Convention Center in San Antonio on Wednesday, Aug. 10, 2011. (AP Photo/San Antonio Express-News, Lisa Krantz) The Associated PressMcALLEN, Texas (AP) — Texas Gov. Rick Perry has many rock-solid conservative credentials. But he may have an Achilles' heel on immigration.If Perry runs for president, as is widely expected, he will undoubtedly focus on Texas' relatively healthy economy, its low taxes and his record in creating jobs in the 11 years he's been governor.What he may find himself explaining is how illegal immigrants have contributed to that success, adding tens of billions of dollars a year to the state gross product and enjoying such benefits as in-state tuition at public universities.Some tea party conservatives who like Perry on other issues would oppose him on this. One anti-immigration activist in North Carolina says Perry is part of the problem.Perry's spokeswoman says he's been a strong advocate for border security.