“For some families, it’s heating or eating. It’s a corny phrase, but it’s absolutely true,’’ said David Bradley, executive director of the Washington, D.C., advocacy group National Community Action Foundation, which is pushing for full federal heating assistance funding. “You can be against big government and deficit spending and be angry, but when you talk about a vital resource, a lifeline to the communities, this is it.’’

While Congress is tied up debating tax cuts and deficits, the program has temporarily been given preliminary funding of $2.7 billion. Massachusetts has been allotted $100.5 million, down from $197.6 million last year. If lawmakers restore full funding, that amount — and the maximum amount of aid to families this winter — would probably go up.

“With family budgets stretched to the limit right now, this is exactly the wrong time to cut back on this program,’’ Kerry wrote in an e-mail to the Globe.

Governor Deval Patrick and Senators John Kerry and Scott Brown have signed letters pushing Congress to allot at least $5.1 billion to the Low Income Home Energy Assistance Program — the same as last year.

Requests for fuel assistance, meanwhile, have swelled in Massachusetts during the economic downturn, from 180,000 three years ago to about 250,000 last winter. Those numbers are expected to rise again this year, to at least 270,000, according to Action for Boston Community Development Inc., one of the agencies that helps low-income families get federal heating assistance. This year, a family of four with an income of $22,050 or less qualifies for the maximum amount of aid.

The decrease in assistance comes as the cost of heating is expected to grow. In the Northeast, the average household is expected to spend $2,201 to heat with oil this winter, or $259 more than last winter, according to federal energy forecasts. Those who heat with natural gas are likely to spend $1,153, or $120 more.

Until it does, agencies that dole out federal heating assistance checks have limited funds available, despite forecasts of a colder winter in the Northeast, rising energy prices, and more people in need. The poorest families are currently getting a maximum of $515 for the winter, drastically less than last year’s $1,240.

And not just for McDonald, but for thousands of others in Massachusetts, who will also struggle to keep the heat on all winter long. McDonald gets help from a federal home heating assistance program, but Congress still has to finalize its funding.

“I try to conserve,’’ said McDonald, 50, a single dad who works three jobs to support his Dorchester family. “It can be tough.’’

Every night before he goes to bed, Richard McDonald checks on his two children to make sure they’re sound asleep. He goes into their rooms, piles on the blankets, and heads downstairs to turn down the heat. He’s hoping he won’t ever have to turn it off.

John Wells, vice president of real estate and energy services at Action for Boston Community Development, said most of the agency’s heating assistance clients are likely to run out of benefits by Christmas if Congress doesn’t act. “We’re not anywhere near where we need to be to get clients through the winter,’’ he said.

The agency has received 16,063 applications for fuel assistance, outpacing last year’s numbers by at least 10 percent. Staff members often check the weather forecast, knowing the coldest days are likely to bring in more people seeking help.

The agency’s clients are single mothers and fathers, low-income families, the elderly, the working poor, and more now than ever, those who have been laid off and were unable to find work before their unemployment benefits ran out. Earlier this week, as temperatures plunged — hovering around 30 degrees during the day, and often under 20 degrees at night — people lined up at the agency’s Tremont Street office in Boston. At times, the line was a dozen deep.

Joshua Arroyo, a father of two, was among those in a yellow-walled waiting area, listening for a counselor to call their names. Arroyo said he lost his job as an operating room technician about a year ago and now depends on a $300 monthly welfare check. He is worried about paying for heating oil for his $950-a-month rental home in Roxbury.

“I feel kind of embarrassed because I have always worked,’’ Arroyo said. “But sometimes it’s OK to raise your hand and ask for help.’’

Linette Duncan of Mattapan said she decided to visit Action for Boston Community Development because she lost her job drawing blood on the day before Thanksgiving. Her unemployment benefits haven’t yet kicked in, and she’s already behind on her natural gas bill.

She later qualified for $310 in assistance; Arroyo will get $455 for the winter.

Kathleen Tobin, the agency’s energy programs director, said it can be difficult to persuade people to get help with their heating bills. She said low-income families often set their thermostats very low — between 50 and 60 degrees — hoping to stave off high heating bills.

McDonald, the single dad, remembered that he first had to ask for help with his heating bill several years ago, after moving to Dorchester with his two children. The winter heating bills for the three-bedroom duplex quickly overwhelmed McDonald, who earns just over $18,000 working at U-Haul, Shaw’s supermarket, and cleaning his church. Before he got any assistance money, he often turned the heat off at night.

“There were times I needed oil, and I almost had to beg,’’ he recalled, adding that he asked for heating assistance because of his children. This year the family qualified for the maximum $515 in aid. He estimates he pays about $400 a month for heat.

Even with assistance, the family conserves. The thermostat is often set at only 58 degrees so the McDonalds will have enough heating oil when the coldest part of winter sets in.

On Monday evening, when the temperature was 30 degrees outside, Richard McDonald wore a blue long-sleeved fleece pullover to ease the chill inside as he and his children decorated their Christmas tree. His 9-year-old son Darius wore thermal pajamas and a bathrobe, while 18-year-old daughter Erica had on a grey thermal shirt.

Darius took the cooler temperatures in stride, saying his dad gets creative about how to stay warm.

“One time, we had hot chocolate,’’ said Darius, as he cut out a paper snowman that he’d drawn.

And when his dad turns down the heat at night, Darius said, he barely notices.

“When I’m in bed,’’ he added, “I’m under the covers.’’

Richard McDonald said he usually wakes up early to turn up the thermostat, warming the house before his children wake up.

“I have to feed them and clothe them and give them a living,’’ he said. “It has to work.’’

Erin Ailworth can be reached at eailworth@globe.com.

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