As she completed a breathing treatment one recent afternoon, Willie Mai Ridley, a 68-year-old beautician, said she would have sought care for her bronchitis in a hospital emergency room were it not for the new clinic. Instead, she took a short drive, waited 15 minutes without an appointment and left without paying a dime; the clinic would bill her later for her Medicare co-payment of $18.88.

Ms. Ridley said she appreciated both the dignity and the affordability of her care. “This place is really very, very important to me,” she said, “because you can go and feel like you’re being treated like a person and get the same medical care you would get somewhere else and have to pay $200 to $300.”

As governor of Texas, Mr. Bush came to admire the missionary zeal and cost-efficiency of the not-for-profit community health centers, which qualify for federal operating grants by being located in designated underserved areas and treating patients regardless of their ability to pay. He pledged support for the program while campaigning for president in 2000 on a platform of “compassionate conservatism.”

In Mr. Bush’s first year in office, he proposed to open or expand 1,200 clinics over five years (mission accomplished) and to double the number of patients served (the increase has ended up closer to 60 percent). With the health centers now serving more than 16 million patients at 7,354 sites, the expansion has been the largest since the program’s origins in President Lyndon B. Johnson’s war on poverty, federal officials said.

“They’re an integral part of a health care system because they provide care for the low-income, for the newly arrived, and they take the pressure off of our hospital emergency rooms,” Mr. Bush said last year while touring a clinic in Omaha.

With federal encouragement, the centers have made a major push this decade to expand dental and mental health services, open on-site pharmacies, extend hours to nights and weekends and accommodate recent immigrants  legal and otherwise  by employing bilingual staff. More than a third of patients are now Hispanic, according to the National Association of Community Health Centers.