For political fund-raisers, the Thanksgiving-to-New Year's period has traditionally been a dead part of the year, and so it was in 1980 for the Democrats, after their losses in the November elections.

Individual donors gave only $174,777 to the Democrats' three national party committees between Nov. 25 and Dec. 31.

But the same five-week period was quite different for the Republicans. While the Democrats were in shock, the GOP's top three national committees harvested 30 times as much in individual contributions: $5,231,777.

Reports to the Federal Election Commission show a stunning Republican performance in the entire 24-month 1980 election cycle that began Jan. 1, 1979, although their lead over the Democrats was less than in the end-of-the-year period.

The Republican National Committee (RNC), the National Republican Congressional Campaign Committee (NRCCC), and the National Republican Senatorial Campaign Committee (NRSCC) raised a combined $108.9 million from individual donors -- nearly six times the receipts of the counterpart Democratic units.

It may be true that everybody likes a winner, but it's also true that no liking of winners begins to account for the Republican success. Rather, the explanation is mainly in plain professional smarts.

"They identified the problem early and moved in," California Congressman Tony Coelho, the new chairman of the Democratic Congressional Campaign Committee, said. "They disciplined themselves. . . . We didn't get our act together."

The starting point for the GOP was the early 1970s, when Watergate had cast a pall over the party's fund raising. The NRCCC, for example, entered 1975 with only about 20,000 active (repeat) contributors, and with a $500,000 deficit. But it ended the year with more than 100,000 active donors and a $1.5 million surplus.

This reversal of fortune was achieved under a new chairman, Rep. Guy Vander Jagt of Michigan, and a new staff led by executive director Steven F. Stockmeyer and finance director Wyatt A. Stewart. Their leadership has brought the number of active donors today to between 700,000 and 800,000, a nearly 40-fold increase in six years. Similar successes followed at the RNC, under Bill Brock, and at the NRSCC, under Sen. Bob Packwood of Oregon.

"They're better organized," Democrat Coelho acknowledged. Even more bluntly, Richard P. Conlon, executive director of the Democratic Study Group, an organization of the party's liberals, said that compared with the GOP, "We're in the Stone Age when it comes to fund raising."

The GOP leaders synchronized the fund raising of the three committees. They coordinated direct mailings under an annual master schedule. They took care not to resolicit recent donors too quickly.

They operated on the basic assumption that direct-mail fund raising was not something that only right-wing groups could do well. They discarded conventional fund-raising wisdom, such as the belief that the summer months were a dead period. "We don't buy that stuff here," Stewart said. Instead, he recalled, summertime was perceived as a fund-raising vacuum to be filled. Even the July 4 holiday became an important solicitation time.

The dimensions of the payoff are shown by the figures for 1980, when, Stewart said, a mailing from one or another of the three committees went out each 20 days or so and brought in about $75 million from some 2 million persons. "At least 90 percent came as an average donation of $20 to $25," he said. By contrast, the Democrats "didn't worry about direct mail," Coelho said.

Stewart figures that the committees net $3 to $4 for every $1 they spend. "There's not a business in the world that does that well," he said.

Both Stewart and Stockmeyer emphasized the huge collection of funds in the post-election period was the result of careful planning. For example, the NRCCC prepared a fund-raising letter to go out after the election. When the outcome of the House races became known, the text was adjusted to reflect it. "It was poised, ready to go," Stewart said.

In the full two-year election cycle that ended last Dec. 31, individual donors gave $61.2 million to the RNC, $27.2 million to the NRCCC, and $20.5 million to the NRSCC. The figures for the counterpart Democratic units were $15.1 million, $1.65 million, and $2 million.

Strikingly, the Republican units got $1 million less from political action committees than did the Democratic ones: $1.4 million as against $2.4 million.

Under the federal election law, an individual may contribute up to $25,000 in each calendar year, including up to $20,000 to the national party committees. By contrast, he can give only $1,000 to a candidate for a primary, runoff, general, or special election, and only $5,000 a year to PACs.

The law puts no ceiling on PAC spending. In 1979-1980, FEC data show, all PACs together raised $127.3 million. This was only $18.4 million more than the combined receipts of the three national Republican committees.

The GOP's fund-raising advantage will help its effort to capture the House in 1982. "We are up against it," said the DSG's Conlon. He and Coelho foresaw a Democratic effort to shift the balance with mass mailings of fund-raising appeals. "We intend to work at it," the congressman said.

Meanwhile, the GOP effort is unrelenting. In a fund-raising letter dated only one day after his inauguration, President Reagan said that winning control of the House is his party's "No. 1 priority." This angered the House Democratic leadership, which was just then organizing support for Reagan's initial official request to Capitol Hill (for an increase in the national debt ceiling).

House Majority Leader Jim Wright protested to the White House that in his inaugural address Reagan had "appealed to the nation to all hang in there together . . . "

The White House apologized Feb. 5, telling Wright that Reagan was "aghast" that the letter had gone out after the election rather than before it, as the president had understood it would.