ASHINGTON, June 14 - As Republicans try to cloak President Bush in the mantle of Ronald Reagan, their biggest obstacle may be Mr. Reagan's own family.Even before Mr. Reagan died, Nancy Reagan and her daughter, Patti Davis, made their opposition to Mr. Bush's policy on stem-cell research well known. But on Friday, at the culmination of an emotional week of mourning for the former president, his son Ron Reagan delivered a eulogy that castigated politicians who use religion "to gain political advantage," a comment that was being interpreted in Washington as a not-so-subtle slap at Mr. Bush.The remark has provoked...