How time flies. Only a year ago, House Republican leader Robert H. Michel (Ill.), flush from a successful alliance with southern Democrats that pushed President Reagan's program through Congress, seemed more like a majority than minority leader.

Last week, as 26 new House Democrats joined their colleagues in the organizing caucus for the next Congress, it was back to business as usual, with Republicans sulking on the sidelines, bemoaning their underdog status.

The immediate cause for complaint was a flurry of rules changes adopted by Democrats in four days of closed-door meetings. "These new rules extend years of steady and systematic assaults on free and open debate and the rights of the minority in the House," thundered a press release on Michel's red, white and blue stationery. " These rules muzzle the membership."

Republican Whip Trent Lott (Miss.) complained on the floor, "The Democratic caucus is once again making a mockery of its party label by proposing undemocratic House rules . . . ."

Robert S. Walker (R-Pa.) called the new rules "legislative tyranny" and a "power grab."

Several of the proposed rules could make it more difficult to pass legislation favored by conservatives, including restrictions on abortion and a constitutional amendment forcing a balanced budget.

The changes, expected to be adopted by the full House the first week in January, would:

* Require signatures of two-thirds, rather than a majority, of members on discharge petitions for constitutional amendments. This would make it more difficult for amendments held up in committee, such as those on balanced budget, busing and abortion, to reach the floor.

* Help block legislative riders to spending bills by requiring that straight money amendments be voted on first, then allowing a motion to "rise" -- cutting off amendments -- to be in order. Thus, a majority could decide not to take up such controversial issues as whether funds in a bill should not be spent for abortions, or, for example, for class-action legal aid suits.

* Allow the speaker to put off routine votes on approving the journal of the previous day and on consideration of bills requiring a quorum. These procedural votes are a nuisance for members called from their offices, but they help Republicans count how many GOP members are in town for an important vote.

Automatically kick a member off his committees when he changes party in mid-Congress. Thus, the threat of losing seniority would encourage party loyalty.

Democrats do not deny that the proposals are designed to give the leadership more power, a move resulting in part from many members' frustration with an increasingly decentralized House where it is difficult to accomplish anything. "We've tended to drift," said Martin Frost (D-Tex.), who headed a rules task force. "People are looking for stronger leadership."

Frost said the rules are fair. "After all," he added, "we are the majority party. We can't let the minority dictate the terms of how the House is run."

Caucus chairman Gillis W. Long (D-La.) said, "We're trying to make the institution operate more effectively. That doesn't abuse anyone's rights."

Nonetheless, two of the proposals prompted heated debate among Democrats. The vote was 121 to 85 on the constitutional amendment rule, and 158 to 50 on the appropriations rider measure, members said.

On the amendment issue, many Democrats reportedly agreed with the statement of Michel and Republican leaders that the new rule is "an outrageous attempt to prevent any consideration of constitutional change that does not conform with the will of the Democratic leadership."

However, Democratic leaders remember the unpleasant surprise served up to them shortly before the election recess when Reagan supporters suddenly rounded up enough signatures on a discharge petition for a balanced-budget amendment to bring it to the floor in an effort to embarrass Democrats. The amendment was defeated because, in the haste to bring it up, Republicans had not rounded up the two-thirds necessary to pass it.

Opponents of the rule expect to win a separate vote on it Jan. 3.

On the appropriations riders, liberals such as Gerry E. Studds (D-Mass.) argued against the restriction because it would curtail legislation regardless of ideological bent. Many recalled that the first anti-Vietnam war measures were appropriations riders.

Last week, a rider on the defense appropriations bill limited the administration's spending for the so-called "secret war" against Nicaragua's leftist government. In recent years, however, riders have been a favorite tool of the new right to limit busing and abortion.

The rider measure is "a gag rule," complained John B. Breaux (D-La.), a conservative who threatened to fight it in the full House. "I understand that members may not like to vote on extremely controversial amendments, but after all these are the issues the nation elected us to legislate."

The disciplinary measure ousting a member from his committee when he changes parties was sparked by Pennsylvania Democrat Eugene V. Atkinson's switch to the GOP. He retained his Democratic seat on the Public Works Committee.

In another party loyalty issue, the caucus voted that "to maintain membership in good standing" in the caucus, Democrats could not participate in campaign activities for Republicans running for federal office. The rule, which does not carry specific penalties, was prompted by Iowa Democrat Berkley W. Bedell's endorsement of Delaware Republican Thomas B. Evans Jr. and several other incidents.

The principal disciplinary fight will take place next month when the caucus votes on committee assignments. Democrats are expected to oust Phil Gramm (D-Tex.) from the Budget Committee for sponsoring Reagan's budget program, despite a promise to Democratic leaders that he would support them on the floor.

Freshmen Democrats and some of the more liberal members would like to deny Gramm his seat on the Energy and Commerce Committee. In a meeting last week, the freshmen, many of whom covet a seat on that committee, unanimously voted to support the move to oust Gramm from both committees. Democratic leaders oppose taking him off Energy and Commerce, arguing that he would surely switch parties.

In other action, the caucus voted to:

* Allow the chairman of the District of Columbia committee, in this case Ronald V. Dellums (Calif.), to chair a subcommittee of another committee. Democratic leaders feared that if they applied the usual rule, they would have a hard time finding anyone to chair the D.C. panel.

Dellums is in line for a subcommittee chairmanship on Armed Services although, to be elected, he must win the support of Pentagon spending advocates he has alienated.

* Permit the Appropriations, Armed Services and Intelligence committees to vote to close as many as seven days of hearings on a single vote. Now they can only close two days at a time.

* Commit themselves to producing "a comprehensive legislative alternative to the president's economic policies" by March 15.