Lee Celano for The New York Times

House Democrats were thrilled by the passage of their major health care legislation, but perhaps no development on Saturday tickled them more than winning the vote of a single Republican: Representative Anh “Joseph” Cao of Louisiana.

Mr. Cao (pronounced gow; rhymes with cow), a freshman from New Orleans, was elected last year in an upset victory over Representative William J. Jefferson, a Democrat who was under indictment on federal corruption charges at the time and has since been convicted.

“Tonight, I voted to keep taxpayer dollars from funding abortion and to deliver access to affordable health care to the people of Louisiana,” Mr. Cao said in a statement posted on his Web site.

“I read the versions of the House bill. I listened to the countless stories of Orleans and Jefferson Parish citizens whose health care costs are exploding — if they are able to obtain health care at all. Louisianans needs real options for primary care, for mental health care, and for expanded health care for seniors and children.”

In the statement, Mr. Cao also said that he had secured a personal commitment from President Obama on health issues important to Louisiana, including disparities in federal reimbursement rates for Medicaid. And while many Democrats complained that tighter restrictions on insurance coverage for abortions had threatened support for the bill on their side, Mr. Cao said that those tougher restrictions encouraged him to support the bill.

Mr. Cao’s vote offered a rare break in ranks for the House Republican minority, which has tried hard to stay unified on major political issues. On the economic stimulus measure, for instance, the Republicans voted unanimously in opposition.

But it was not the first time Mr. Cao broke with his party. He was one of 29 Republicans to join Democrats earlier this year in voting to reauthorize the Children’s Health Insurance Program.

Democrats, teasingly, immediately claimed a mantle of bipartisanship for their health care legislation.

“This was, as you observed, a bipartisan vote,” the House majority leader, Representative Steny H. Hoyer, Democrat of Maryland, said at a news conference to celebrate the passage of the bill.

Mr. Cao, who made his decision near the end of the 15-minute voting period, quickly slipped out of the House chamber and eluded news reporters. He is certain to enjoy political celebrity in the days ahead, though it is unclear it will help his political prospects.

Democrats are already lining up to challenge Mr. Cao next year, and analysts consistently rate his district is among the most likely to switch to Democrat from Republican control.

Mr. Cao, a lawyer, is a minority in several senses: a Republican amid a crowd of Democrats; a Vietnamese-American in an overwhelmingly black district.

In his election campaign last year, Mr. Cao promised ethics and integrity. He was born in Vietnam (he is the first Vietnamese-American member of Congress) and he fled with two siblings after the Fall of Saigon in 1975, moving to live with an uncle in Indiana.

He holds a master’s degree in philosophy from Fordham University and received his law degree from Loyola University.

His vote in favor of the health care legislation contrasted with the “no” vote by Representative Charlie Melancon, a Democrat from southern Louisiana, who is running for the Senate next year. Senator Mary Landrieu, Democrat of Louisiana, has expressed reservations about the health care legislation, particularly the proposal for a government-run insurance plan or public option. She is being courted aggressively by Senate Democratic leaders who need all 60 members of the Democratic caucus to advance the health care bill.

The only Republican Senator to vote in favor of the health care legislation during the committee process was Olympia J. Snowe of Maine, but Ms. Snowe has since said she will oppose bringing up the bill for debate because the majority leader, Harry Reid of Nevada, added a government plan to the bill.