President Reagan used a Memorial Day political fund-raiser here today to launch a sharply worded attack on Democrats, accusing them of ignoring the dangers of communism abroad and "pitting white against black, women against men, young against old" at home.

Speaking to 1,600 contributors to Sen. Paula Hawkins (R-Fla.), Reagan appealed for continued Republican control of the Senate with pointed criticism of Democrats on the issue of defense spending.

"The opposition often acts like a weaker America is a safer America," he said. "Like it or not, that's the kind of bizarre logic that will carry the day if the other party regains control of the Senate."

The president's sharply partisan attack came after a string of setbacks for Reagan initiatives on Capitol Hill, and on the eve of his new crusade for tax simplification that, according to his political strategists, will succeed only if it gets bipartisan support.

In his speech Reagan accused political opponents of ignoring communist dangers in Nicaragua.

"Many of those opposing our efforts have steadfastly refused to acknowledge that the rulers of the regime in Managua are, by their own admission, hard-core communists and consider themselves part of the international communist movement," Reagan said.

"Nicaragua today equals aggression, pure and simple," he added.

Reagan departed from his prepared text to comment that citizens are confused about the Nicaraguan conflict and declared, to applause, "It's the freedom fighters against the communists."

"Closing our eyes and making a wish, which seems about the only course of action our opponents will support, won't make this threat go away," Reagan said. "We need to assist those governments targeted by the communists, and it is imperative that we support those brave individuals who are putting their lives on the line to bring democracy to Nicaragua."

Opening his speech to contributors who paid up to $1,000 each for Hawkins at the plush Omni Hotel here, Reagan said Republicans "have been blessed with grass-roots supporters who are committed to the ideals of individual freedom, family values, free enterprise and a strong America."

"While the other party has tried to build a coalition by segmenting America into warring factions -- over the past years pitting white against black, women against men, young against old -- we've taken a more positive path," he said.

This remark was almost identical to one that former president Jimmy Carter made in the 1980 campaign, touching off a furor. Carter said if he lost the election, "Americans might be separated black from white, Jew from Christian, North from South, rural from urban." After Reagan called on Carter to apologize, Carter said the stridency of his remark was a mistake.

"We don't promise quota systems and giveaway programs," Reagan said today. "We promise to do what is right for America and for all Americans."

Reagan's partisan criticism follows a series of congressional defeats for his military buildup and his effort to provide aid to the rebels fighting the Sandinista government of Nicaragua.

Reagan has been opposed on both fronts from Republicans as well as Democrats. For example, the Republican-controlled Senate, where 22 GOP members face reelection next year, voted to hold Pentagon spending increases to the level of inflation for next year; the Democratic-controlled House voted less.

Reagan today renewed the administration's charge that Cuba has been engaged in drug trading. "I have a message for Fidel Castro about the drug trade," Reagan said. "He can tell American television networks anything he wants, but nobody in his regime is going to get away with this dirty drug business."

Reagan, noting that Democrats have no women in the Senate while Republicans have two, paid tribute to Hawkins, citing her "amazing" Senate record.

The senator, who is expected to face a tough reelection campaign against Florida's Democratic governor, Robert Graham, responded in tears today when reporters asked her about a news report that her brother is in jail awaiting trial on child molestation charges.