Rep. James H. Scheuer (D-N.Y.) was in the House chamber yesterday when Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) walked over to make a pitch for the tax-overhaul legislation scheduled to come up next week.

The Ways and Means Committee measure would help the poor, O'Neill told Scheuer, who has not yet decided how he will vote. And politically, O'Neill added, it would be a mistake to have tax overhaul die in the Democratic-controlled House.

Earlier this week, the New York liberal encountered House Majority Leader James C. Wright Jr. (D-Tex.). The tax legislation was again the issue.

When Scheuer told Wright he didn't particularly like the bill and was thinking of opposing it, Wright smiled and told him that he, Wright, was going to vote against it.

As the fight for votes on the tax bill moved to center stage in the House this week, so has the split it has caused between the House's top two Democratic leaders.

All sides downplay it, and Wright apparently has been willing to take an unusually low-key role on the bill in deference to O'Neill. But the public divide between O'Neill and the man he has tapped to succeed him as speaker in a year is, nonetheless, visible and highly unusual.

O'Neill and Wright represent different ideologies -- O'Neill is an old-fashioned New Deal liberal and Wright a Texas moderate -- but in their party posts they have marched publicly in lockstep on almost every major issue.

The tax bill reported by the Ways and Means Committee this week represents a sharp departure from all that, both men conceded yesterday.

"We have been disagreeing on the philosophy on taxes since the beginning of the year," O'Neill said at his regular morning news conference as Wright sat a few feet away.

"The speaker and I have a great working relationship. We agree on 90 percent of the issues," Wright said.

O'Neill has said he is determined to get the tax bill through the House, in part because he thinks that the bill produced by his friend, Ways and Means Chairman Dan Rostenkowski (D-Ill.), is better than current law. He also has said he believes strongly that President Reagan, who has adopted the campaign for "tax reform" as his own, would "clobber" the Democrats politically if the measure fails.

Wright, on the other hand, dislikes aspects of the bill, such as the elimination of some tax breaks for oil companies, including those in his state.

But mostly, Wright said, he thinks a tax-overhaul measure must raise new revenue to reduce the federal budget deficit. The Ways and Means bill, like the proposal submitted by Reagan, is not intended as a net tax increase.

O'Neill said yesterday he agrees that a tax increase to deal with the deficit is needed but that Reagan has made it clear he would veto any such bill and use it against the Democrats in the next election.

"If this nation's going to get a tax [increase] bill while I'm speaker, it's going to come from the president of the United States. When Jim's speaker, it might be different," O'Neill added.

Meanwhile, Wright said he expects to stay out of the fight over the tax bill, except to explain to colleagues, such as Scheuer, why he will vote against it.

"I'm not taking an out-front role. I'm not beating the drums," he said. "I'm not trying to undermine the speaker or Danny [Rostenkowski]. I don't have to be in the middle of every fight."

Several lawmakers and officials said yesterday that in addition to dodging direct confrontation with O'Neill, Wright was eager to avoid conflict with Rostenkowski, who has said he might be interested in running for speaker when O'Neill retires at the end of 1986.

Even if Wright is a shoo-in to become speaker, as it now appears, Democrats said yesterday that he would not want to sour his relations with Rostenkowski. "He doesn't want to poison the well," said one Democrat. "If the bill goes down and Jim Wright had worked against it, Rostenkowski is going to remember that. He comes from the school of politics [in Chicago] where you don't forget."