The Republican Party yesterday announced that it would keep its "Operation Open Door" open a little longer and change the rules a bit amid signs that the four-state campaign to switch the registration of 100,000 Democrats in 100 days had fallen short of its goal.

Democrats could hardly contain their glee.

"Given the ton of cash they spent they should have been able to reregister 100,000 people as Mugwumps or Whigs," said Democratic National Committee spokesman Terry Michael. "It looks like they're getting the open door slammed in their face."

Republican National Committee spokesman William I. Greener III, however, called the campaign, announced May 7 with great fanfare, "a success."

"We have 100,000 switches," he said. "We're over that [number]."

When they launched Operation Open Door, Republicans set a goal of converting 45,000 Democrats in Florida, 25,000 in Louisiana and 15,000 in both North Carolina and Pennsylvania within 100 days.

Although the 100 days ended yesterday, Greener, in charge of RNC political operations, said his party would keep working and announce the results, with documentation, at a news conference next Thursday.

But the figures won't necessarily represent converts. Greener said Republicans will count reregistrations and signed cards from Democrats indicating an intention to switch parties.

"It looks like they are changing the rules in the middle of the game and using funny numbers," Democratic spokesman Michael charged, obviously relishing the GOP's embarrassing situation.

"Democrats are so used to cooking numbers and playing with smoke and mirrors they don't know reality," Greener retorted in an interview. "The fact of the matter is Republicans are winning and Democrats are losing voters all over the country. That's reality."

It was unclear yesterday how many Democrats have switched. Newspaper surveys of election officials in two states -- North Carolina and Florida -- indicate Republicans were falling far short of their goals.

The Tampa Tribune reported that as of Tuesday only 6,340 Democrats had switched in 13 targeted Florida counties, where Republicans had concentrated their efforts.

Only 320 converts were reported in Dade County (Miami), the state's most populated area. The vice president's son, Jeb Bush, is GOP chairman there.

Republicans mailed out 400,000 letters and hired solicitors to go door-to-door in search of converts in Florida. The solicitors were paid $4.50 an hour and given a $5 bonus for every convert they found.

The Charlotte Observer reported that its survey of election officials in all 100 North Carolina counties found only 2,130 Democratic switches between May 7 and Aug. 6.

Greener said yesterday that the GOP will meet its goals in North Carolina, Louisiana and Pennsylvania, but "fall short in Florida." The 100,000 figure would be reached, he added, by counting switchers from elsewhere in the country.

The four states states were picked originally because each has a Senate contest in 1986 and because voters register by party, making it possible to track results. In addition, recent registration trends in all but Pennsylvania favored the GOP.

But the effort turned out to be far more difficult and expensive than anticipated. The budget for the campaign jumped from $500,000 to $750,000.

Efforts were late in starting in some areas. Hastily trained door-to-door solicitors in Florida found it difficult to find people at home during the summer. In North Carolina, voters had to go in person to county election offices to switch parties.