WASHINGTON — The Am­erican public has enormous confidence in the progress being made against cancer and its faith is translating into overwhelming support for the Obama administration’s proposal to increase cancer research spending, a new STAT-Harvard poll finds.

More than 8 out of 10 Americans support at least a 20 percent increase for federal cancer research funding, the amount the president has requested for what the administration is calling the National Cancer Moonshot, which is being led by Vice President Joe Biden. According to the poll, 46 percent said the funding increase is “about right,’’ while 37 percent said it’s not enough.

Backing for Obama’s “moonshot’’ was bipartisan, with 90 percent of Democrats and 79 percent of Republicans supporting at least a 20 percent boost in cancer research spending.

The findings suggest that Obama and Biden can count on broad support for the cancer funding — as long as they and the Republicans who control Congress can agree how to pay for it.

Obama wants the $755 million increase he has proposed for next year to come from an automatic funding stream, called “mandatory’’ spending, but top Republicans say that would allow him to do an end run around the spending limits written into federal law. They would rather use the regular funding process, which they say would give Congress more control.

The poll, by STAT and the Harvard T.H. Chan School of Public Health, found that two-thirds of Americans think cancer treatments are more successful than they were 10 years ago at allowing people to live longer with a good quality of life.

That’s true for some people, but not for everybody. New therapies are helping only 10 to 15 percent of patients live longer lives, said Dr. Otis Brawley, chief medical officer at the American Cancer Society.

“Some of these people have amazing quality of life,’’ Brawley said. “The frustration right now is that we can’t do it for everybody.’’

The optimism about cancer treatment stands in stark contrast with the electorate’s generally sour mood: 7 out of 10 Americans in a Gallup poll this month said they’re dissatisfied with the way things are going in the United States.

“So this is really quite unusual, in that there’s a real sense that progress is being made [against cancer] in a country where there’s real skepticism that anything is getting better,’’ said Robert Blendon, a professor of health policy and political analysis at Harvard who oversaw the poll.

That sentiment is probably driving the support for cancer research funding, Blendon said.

Nearly half of those polled — 47 percent — said cancer is the most serious disease or health condition in the United States today. The rest weren’t even close: 11 percent said heart disease was the most serious, 8 percent said diabetes, and obesity and HIV/AIDS came in at 6 percent each. Only 3 percent picked Alzheimer’s disease, despite all the attention it’s getting from lawmakers and advocacy groups in Washington.

Zika virus, the mosquito-borne illness that’s been in the headlines because of its suspected link to birth defects and neurological problems, was mentioned by just 2 percent.

Heart disease is the leading cause of death in the nation, with cancer a close second, according to the Centers for Disease Control and Prevention.

The poll was conducted for STAT and Harvard by SSRS, which interviewed 1,000 randomly selected US adults by telephone from March 2 to 6. The margin of error was plus- or minus-3.7 percentage points.

A report this month from the National Cancer Institute found that overall cancer death rates declined by 1.5 percent between 2003 and 2012, though that was largely because of advances in prevention and early detection.

David Nather can be reached at david.nather@statnews.com.