In the town of Lehi is the sprawling headquarters of Xango, where company officials praised Mr. Hatch, a Utah Republican, late last year for helping their exotic fruit juice business ?operate without excessive intrusion? from Washington.

Up in Sandy, Utah, is 4 Life Research, whose top executives donated to Mr. Hatch?s last re-election campaign after federal regulators charged the company with making exaggerated claims about pills that it says helps the immune system. And nearby in West Salem, assembly-line workers at Neways fill thousands of bottles a day for a product line that includes Youthinol, a steroid-based hormone that professional sports leagues pushed to ban until Mr. Hatch blocked them.

?Senator Hatch ? he?s our natural ally,? said Marc S. Ullman, a lawyer for several supplement companies.

Mr. Hatch, who credits a daily regimen of nutritional supplements for his vigor at 77, has spent his career in Washington helping the $25-billion-a-year industry thrive.

He was the chief author of a federal law enacted 17 years ago that allows companies to make general health claims about their products, but exempts them from federal reviews of their safety or effectiveness before they go to market. During the Obama administration, Mr. Hatch has repeatedly intervened with his colleagues in Congress and federal regulators in Washington to fight proposed rules that industry officials consider objectionable.

While Congress is often stalled or bitterly divided in addressing some of the nation?s most pressing problems, like the economy and immigration, legislative champions like Mr. Hatch are often remarkably successful in delivering for niche industries or parochial programs. It is not unusual, of course, for lawmakers to fight for local interests, but Mr. Hatch?s alliances are particularly strong and mutually beneficial.

Mr. Hatch has been rewarded with hundreds of thousands of dollars in campaign contributions, political loyalty and corporate sponsorship of his favorite causes back home.

His family and friends have benefited, too, from links to the supplement industry. His son Scott Hatch, is a longtime industry lobbyist in Washington, as are at least five of the senator?s former aides. Mr. Hatch?s grandson and son-in-law increase revenue at their chiropractic clinic near here by selling herbal and nutritional treatments, including $35 ?thyroid dysfunction? injections and a weight-loss product, ?Slim and Sassy Metabolic Blend.? And Mr. Hatch?s former law partner owns Pharmics, a small nutritional supplement company in Salt Lake City.

But many public health experts argue that in his advocacy, Mr. Hatch has hindered regulators from preventing dangerous products from being put on the market, including supplements that are illegally spiked with steroids or other unapproved drugs. They also say he is the person in Washington most responsible for the proliferation of products that make exaggerated claims about health benefits.

Just in the last two years, 2,292 serious illnesses, including 33 that were fatal, were reported by consumers of supposedly harmless nutritional supplements, federal records show. (These ?severe adverse reaction? reports do not necessarily mean the supplements caused the illnesses, just that the consumers became ill after taking them.) And some of Mr. Hatch?s most important supporters in Utah have faced repeated accusations of falsely claiming their products can treat almost everything, including cancer and heart disease.

?Orrin Hatch certainly has a right to fight for his constituents,? said Steven Novella, a clinical neurologist at the Yale School of Medicine who was a co-founder of a Web site that tracks claims by the supplement industry. ?But the consequences are we have an effectively unregulated market for these products, a Wild West, and people are being abused by slick marketing, and as a result taking things that are worthless or in some cases not even safe.?

Mr. Hatch rejects such accusations, noting that he has repeatedly demanded that federal regulators step up enforcement of existing laws, and even worked to expand their powers.

?No relationships have or will ever have any impact on my policy positions,? Mr. Hatch said in a written statement. ?Supplements are healthy and safe, and they are a major industry in my home state of Utah.?

The depth of his industry support could be put to a test over the coming year, as Mr. Hatch prepares for what could be a tough re-election fight if Representative Jason Chaffetz, a Republican, mounts a primary challenge. Mr. Chaffetz, a former executive at a Utah company that sells anti-aging and skin care products, is also an industry ally.

Several executives, though, say they cannot imagine turning their back on Mr. Hatch.

?Some folks get elected, go to Washington, forget where they came from,? John F. Gay, chief executive of an industry trade association, said last year in introducing Mr. Hatch at an industry convention in Las Vegas. ?Others get elected, go to Washington, and use the knowledge they have gained, the relationships they?ve built, the power they have developed over the years of incumbency to help the folks who got them there. That is the type of person that Senator Hatch is.?

Hatch to the Rescue

Kitty Bennett contributed research.

This article has been revised to reflect the following correction:

Correction: June 21, 2011

An earlier version of this article rendered the name of an advocacy group incorrectly. It is Citizens for Responsibility and Ethics in Washington, not the Center for Responsibility and Ethics in Washington.