President Carter's massive welfare bill appears dead for this Congress, the victim of its own $20 billion price tag, the pressure of time and differences within Congress over welfare policy.

Carter's proposed has been lauguishing for months. Now even some of its most ardent backers have given up hope that it can pass either the House for the Senate this year. Instead, they are trying to put together with the Carter administration a vastly cut-down version, costing $4 billion to $5 billion a year above current programs instead of the $20 billion that the Carter bill would add to existing programs. Even that kind of package might not get through Congress this year.

The cut-down version probably would include:

Boosting the current 10 percent Treasury wage supplement of earnings to 13 percent or 15 percent.

Making families with unemployed fathers eligible for welfare, if the overall family income is low, all over the country. Currently only half the states allow welfare where an unemployed father is involved.

Imposing a minimum benefit for a faimly with children, perhaps equal to $4,000 or $4,200 in cash and food stamps for a family of four. At present about 10 states pay less. Mississippi, for example, pays only about $3,100.

The Carter welfare bill was left off a "priority" list of legislation to be considered in the House for the remainder of this year, complied Speaker Thomas P. (Tip.) O'Neill Jr. (D-Mass.) and shown to President Carter at the White House Tuesday. That means that the bill almost certainly won't reach the House floor.

Rep. Charles B. Rangel (D-N.Y.), a key supporter of the measure, said yesterday that the bill is not on President Carter's priority list for passage this year.

House Majority Leader Jim Wright (D-Tex.) said yesterday that "It seems improbable to me, given the time in the session and the other things stacked up ahead of it, that it can ever reach the floor."

Even if it did come up, most vote-counters predict that it would lose, primarily because of its cost.

In the Senate, the prospects are even worse. Finance Committee Chairman Russell B. Long (D-La.) and the majority of his committee oppose the Carter bill.

Majority Leader Robert C. Byrd (D-W.Va.) also compiled a list of "priority" legislation for the rest of this session for the Tuesday meeting at the White House, and it also did not include Carter's bill.

Sen. Daniel Patrick Moynihan (D-N.Y.), the bill's Senate sponsor, said as far as he knows the Carter measure only has "one certain vote in the Finance Committee - me."

A source at the Department of Health, Education and Welfare, which drafted the Carter bill, said meetings are going on to try to draft some compromise which Moynihan, Secretary of HEW Joseph A. Califano Jr., the President, House sponsor James C. Corman (D-Calif.) and other key leaders might be willing to try to push through this year, but "it will be cut back."

The Carter bill proposes federalization of the entire basic welfare program, an increase in wage supplements, a $4,200 national minimum, 1.4 million "last resort" jobs for welfare clients at a cost of $8 billion or more, and extension of welfare benefits not only to unemployed fathers but to single persons and childless couples who are poor, even if they aren't aged, blind or disabled.

The Congressional Budget Office said in a report released yesterday that nearly seven in 10 poor families would receive increased benefits under Carter's plan, while 10.8 percent of poor families would receive less.

The study said Carter's plan, as proposed, would add $17.4 billion to welfare costs in 1982. As modified by a special House subcommittee headed by Corman, the plan would add $20 billion in 1982. Existing welfare programs would cost about $25 billion in 1982.