The high tax-cut cards that have always been in Ronald Reagan's hand are gaining value day by day as the portents of disarray among House Democrats harden into fact and the Republican-controlled Senate Finance Committee rushes to finish marking up a Reganite tax bill next week. f

The post-election disorder has led to this curious spectacle: a House Democratic majority, led by the venerable speaker and old-line liberal Thomas P. (Tip) O'Neill, groping for its center of gravity but finding only empty spaces.

"Tip's still trying to decide what his new constitutency is," one of the speaker's longtime Republican friend told us. The result is a babble of confused voices from the Democratic majority, with O'Neill now insisting on a non-Reaganite tax bill tailored to traditional liberal standards without the ghost of a chance of hitting pay dirt.

The first victim of this whimsical strategy is Rep. Dan Rostenkowski, chairman of the Ways and Means Committee, who labored hard to arrange a compromise with Reagan but was shouted down by O'Neill. Rosenkowski hopes to avoid hara-kiri in drafting his Democratic bill, but close friends fear he may be headed for it when he takes the final product to the floor in his maiden effort as committee chairman.

One reason is the president's high cards, now beginning to drop on the table. The opener was his June 16 press conference castigating Democratic delay in the House and warning not to "forget the mandate of November." He'll follow that up with a tax-and-economy speech in San Antonio June 24 and another in Denver on June 29.

At the same time, Reagan is quietly soft-soaping the opposition. He sent Rostenkowski an autographed copy of a front-page picture in the June 1 Washington Star, showing the dejected chairman emerging from the White House, with the message: "Cheer up, Danny." He is also lubricating his allies. The Wall Street Journal published a story about Texas Rep. Kent Hance, the "boll weevil" Democrat who is co-author of the Conable-Hance-Reagan tax bill with Republican Barber Conable. The headline read: "Hance Enrages His Party." Reagan phoned Hance: Don't worry, and don't forget that you and I are together on this.

Even that other old cozy Irishman, Tip O'Neill, got a friendly Reagan call the day after the president denounced the "sheer demagoguery" of O'Neill's labeling Reagan's tax bill a rich man's bill.

Even without the Reagan message, the plight of the Democrats grows. They lack consensus as a party, and they lack it within the party's squabbling factions. Old-style liberals are split, some wanting what one called "a poor man's tax bill" loaded with low-income goodies that could never pass the House but might become a 1982 campaign weapon if the economy turned sour. But savvy Ways and Means Committee member William Brodhead, chairman of the liberal Democratic Study Group, courts political reality, meaning a tidy bill that just might pass the House.

Further immobilizing the House majority is the prospective battle for succession to O'Neill's post, involving Majority Leader Jim Wright, who preferred compromise with Reagan, Budget Committee Chairman Jim Jones and Rostenkowski himself, none of whom is encumbered with old-line, purist liberal ideology.

"We don't know what we want, a bill or an election year issue, because very few of us have thought this puzzle all the way through," one liberal leader told us. The surprise is that, except for the conservative "boll weevils," his colleagues agree.

Enter Sen. Robert Dole and his Senate Finance Committee with strong support from the White House. Dole's Republican-controlled committee plans to complete marking up the modified Reagan tax bill by June 26, taking the lead away from the House (where tax bills almost always originate). He can attach it to a House-passed debt ceiling bill for Senate action whenever he wants.

This tactic, unusual but not unprecedented, will further inflame House Democratic leaders already enraged by Reagan's stepped-up campaign against them. But it will give the president new ammunition to force the House to act.

House Democratic leaders are crying foul play, but Reagan holds the high cards. He seems serenely secure that when the great 1981 tax battle ends, he will walk off with the pot.