Rep. Mickey Leland (D-Tex.), who chairs the Congressional Black Caucus and calls himself "an automatic respondent to the cause of poor and working people," said he badly wants to support the tax-overhaul bill in the House that would remove 6 million low-income Americans from the tax rolls.

But Leland has a problem. His Houston district, while weighted with poor families, is home to more oil companies than any other congressional district. And the Ways and Means Committee's tax bill would pare oil's legendary tax benefits.

The dilemma Leland faces is not confined to representatives from the Southwest or to Democrats. In the Midwest, headquarters of steel and other basic industries, and the Pacific Northwest, center of the timber industry, lawmakers across the political spectrum are balking at a bill that would raise taxes on the biggest employers in their districts.

Those three regions, all reliant on industries that would lose tax benefits under the bill, have in the last week become the most forceful opponents of the measure.

"Regionalism is much more important than ideology," said Rep. Charles E. Schumer (D-N.Y.), who is trying to rally support for the bill. "If you're a liberal from Texas, you're against the bill. If you're a conservative from New York or Massachusetts, you're for it."

White House and congressional leaders predicted yesterday that the measure would be approved by the House, but privately they worried about the regional rancor the bill has unleashed.

"You can talk all day about good tax policy and about how much heavy industry has benefited from the tax laws all these years," said a member of the Ways and Means Committee's staff, "but many of these members' defenses are governed much more by passion than by tax policy."

To puncture the opposition, House members supporting the committee bill have resorted to regional deal-making. According to several sources, House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) has vowed to give consideration to the steel industry in a 1986 trade bill in return for the votes of certain legislators. (Rostenkowski's panel deals with trade as well as taxes.)

Yesterday, several House leaders said that Rep. John Murtha (D-Pa.) of the Johnstown area, had moved from the undecided to the "yes" category. Murtha, renowned for his vote-brokering skills, was expected to bring most Pennsylvania Democrats with him.

"That reassurance gives some cover to members who want to vote 'yes,' but who have some misgivings about steel," said a Democrat familiar with the deal.

However, it was unclear yesterday whether that reassurance would overcome the effect of recent meetings of steel-region lawmakers with officials of Bethlehem Steel and others opposed to the bill. In those sessions, the officials "climbed all over us, saying not to vote for that bill," according to a Democrat who was present.

The task force of 25 Democrats assembled by Rostenkowski to whip up support is trying to break the regional blocs by emphasizing that there is much to be gained -- for certain corporations as well as individuals.

To persuade midwestern members, they have dispatched officials of General Motors, which supports tax overhaul, to remind lawmakers that GM is the largest purchaser of steel in America and hopes to buy even more if the bill passes.

To win over the Pacific Northwest, the task force has told House members not to worry about timber because Senate Finance Committee Chairman Bob Packwood (R-Ore.) will take care his state's biggest private employer in the Senate.

Among those regional loyalists who yesterday remained undecided or were planning to vote "no" were: Rep. Douglas Applegate (D-Ohio), whose Ohio River valley district depends on steel and coal; Rep. Paul B. Henry (R-Mich.), whose Grand Rapids district depends heavily on the machine-tool industry; Rep. Ron Wyden (D-Ore.), whose Portland district relies on timber, and Rep. Mike Synar (D-Okla.), whose sprawling district depends on oil.

"Members from forest products states have got to do everything they can at every step to push for a fair shake for timber," Wyden said. "I want to make sure that this is not a choice between jobs in my district and a tax bill that undeniably has some positive features. That's the real danger for a quite a few of us, and that's why this issue is so fluid."

Even the most persuasive forms of pressure have had little effect. Rep. Bill Schuette (R-Mich.), a freshman from Midland, headquarters of Dow Chemical Co., said he received a call yesterday from Treasury Secretary James A. Baker III. Schuette described Baker as an "old friend" but said he remains inclined to vote "no."

"You'll find no one in my district who quarrels with a simpler, fairer tax system," Schuette said. "But we've got to look at chemicals. We've got to look at timber. Even more, we've got to look at heavy industry. It's a region, it's an entire orientation we're talking about."

In Leland's case, the House task force has rallied numerous liberal Democrats, unions and grass-roots organizations representing the poor to push, in the name of liberalism and fairness, for a "yes" vote from him. But Leland said yesterday, with a wince, that it is not working.

"I think of 6 million poor people across America, but it's rather difficult for me to drop the parochial interest of saving the city of Houston," Leland said. "I have to say I'm leaning against the bill, but it's the toughest issue I've ever faced. My friends stop me all the time to remind me of my liberal instincts -- even when I go on the basketball court in the House gym."

Perhaps the most persuasive argument facing the regionalists is the political fallout in 1986. Suppose these Democrats from blue-collar districts vote "no" and then face opponents who tar them for voting against a bill that promised to cut taxes for individuals and hike them for big business?

"The best position to be in is a challenger when it comes to this tax bill," said an Applegate aide. "Whichever way we vote, there's plenty of ammunition. Hopefully, people vote what's good for the country."