President Reagan campaigned for Republican candidates in Texas and Florida today by blaming Democrats for energy problems, the federal deficit and "unprecedented national pessimism."

Taking a page from the past, when he campaigned as a government outsider, Reagan denounced "big taxers and big spenders" in Washington, drug smugglers, Cuban President Fidel Castro and the Sandinista regime in Nicaragua.

"Believe me, the liberals in Washington know what's at stake in this election," Reagan told a midday rally at the Dallas Apparel Mart. "They know that this may well be their last chance to steer American politics way over to the left. They know that if we Republicans do well this November, it's going to permanently alter the political landscape."

Reagan's speeches here and in Dallas were reminiscent of those he gave a decade ago when he was campaigning against President Gerald R. Ford for the GOP nomination and trying to mobilize conservative audiences with antigovernment and anticommunist themes.

At a rally tonight in this city, where he won the support of the Cuban-American community in 1976, Reagan likened Castro to Stalin. The president said Castro has presided over "a cruel system that . . . produces misery, fear, deprivation and little else."

The crowd responded with loud and repeated chants of "Four more years!" and Reagan ad-libbed a comment that the 22nd Amendment, which prohibits a presidential third term, should be repealed -- not for himself but for future presidents.

The cost of oil and natural gas was Reagan's theme in Texas, where the decline in oil prices has triggered a major economic slump. Reagan took credit for decontrolling the price of oil and said "we will press and press again until Congress passes comprehensive decontrol of our natural gas supplies and takes the other steps we have proposed to protect America's future."

On his first full-scale political trip of the 1986 campaign, Reagan also addressed private fund-raising receptions for GOP candidates. He is attempting to raise $2 million during a two-day, three-state swing.

Today the president campaigned for former Texas governor William P. Clements Jr., who is trying to make a comeback against Gov. Mark White, the Democrat who defeated him four years ago. Here in Miami, Reagan called for the reelection of Sen. Paula Hawkins, whom he described as "a gutsy individual who has played a unique and irreplaceable role putting America back on the right track."

Polls show Clements far ahead of White. Without using White's name, Reagan said he stood for a policy of "tax and tax, spend and spend in Austin." Hawkins is well behind her Democratic opponent, Gov. Bob Graham, in surveys. Reagan made no reference to Graham today but credited Hawkins with "an essential role" in his administration's war on drugs.

"The drug pushers and the merchants of death who supply them are on notice," Reagan said. "The time is right to retire from the trade for health reasons."

A recurring theme in Reagan's speeches today was an emotional denunciation of Nicaragua's government coupled with praise for the "20,000 freedom-fighters who need our help in restoring democracy in that country."

In Dallas the president appealed to Texas chauvinism by saying that "the communist Sandinista regime in Nicaragua has made a lot of mistakes, but even they know better than to get themselves in a tangle with a bunch of Texans."

"Even with all the tanks and gunships from the Soviet Union, my guess is that the Sandinistas would make it about as far as the shopping center in Pecos before Roger Staubach came out of retirement, teamed up with some off-duty Texas Rangers and the front four of the Dallas Cowboys and pushed the Sandinistas down the river, out across the Gulf and right back to Havana where they belong," Reagan said.

Former quarterback Staubach, who was on the stage with Reagan, said, "I've been asked to come back against the New York Giants and the Washington Redskins, but not against the Sandinistas."

The president acknowledged that he obtained support from southern Democrats in winning House passage of a measure to provide $100 million in military and economic aid to anti-Sandinista rebels. But he said it would be easier to muster opposition to the Sandinistas if more Republicans were elected to Congress.

"What's really at stake here is restoring our bipartisan consensus on national security issues; believe me, you'll send that message to the liberals in Washington if you'll elect more Republican officeholders here in Texas," Reagan said.

A small group of protesters opposed to Reagan's South Africa policies attended the rally and shouted at him during the speech. They bore a sign that read: "Sanctions now."