WASHINGTON — Despite two decades of dire health warnings and threats of federal intervention, the specialty drugmakers at the center of the nation’s deadly meningitis outbreak have repeatedly staved off tougher federal oversight with the help of powerful allies in Congress.

Over the years, industry friends like Tom DeLay, the former House Republican leader from Texas, have come to its defense. Even Senator Edward M. Kennedy, regarded as the strongest health care advocate in Congress in recent times, dropped efforts to impose new safeguards.

But the pharmacists known as compounders are now facing their biggest regulatory threat as they confront questions on Wednesday and Thursday at Congressional hearings on the deadly outbreak. The question is whether Congress will move to oversee the niche industry more aggressively.

“A lot of the blame for the meningitis situation lies at Congress’s door,” said Larry D. Sasich, a research pharmacist who has written about compounders’ safety record. For specially mixed drugs that fall into a gray area of federal law, he said, “the protections for your cat or dog are stronger than for your wife and children.”