President Reagan tried to boost the fortunes of Republican gubernatorial candidate Carroll A. Campbell Jr. today by portraying his Democratic opponent as a liberal cut from the same cloth as Walter F. Mondale.

Reagan said the governor's race shaped up as "a replay of the contest between Reagan and Mondale" because Lt. Gov. Mike Daniel, the Democratic nominee, was the 1984 Democratic presidential nominee's "principal spokesman" in the state when Campbell was chairman of the president's reelection campaign.

"This race in South Carolina has national importance," Reagan said. "It pits the new against the old, trust in the people against belief in big government, the sound values of the people of this state against the schemes and social programs of the liberal Democratic leadership," Reagan said at a GOP fund-raising luncheon at the University of South Carolina Coliseum.

Before his speech, Reagan stopped at the Columbia airport to watch bales of hay being unloaded from an Air Force C141 cargo plane to help drought-stricken farmers.

The 24-ton shipment was the latest delivery on a "hay hot-line" established by Illinois Gov. James R. Thompson (R) to send surplus midwestern hay to South Carolina and Georgia. Campbell and Thompson asked the federal government for assistance and Reagan directed that Air Force cargo planes be used in the relief operation.

But Sen. Ernest F. Hollings (D-S.C.) charged in Washington on Wednesday that the Reagan administration was "playing politics with our disaster relief." Hollings said that when he asked for an Air Force plane to transport 30 tons of hay from Massachusetts he had been turned down by Andrew Cord, acting White House director of intergovernmental affairs. A White House spokesman said that about 2,000 tons of hay are being flown in from the Midwest and that it would "not be cost-effective" to fly in 30 more from Massachusetts.

Hollings, running for reelection, is favored over Republican nominee Henry McMaster. The president made no critical reference to the popular Hollings but said it was important to keep the Senate in Republican control so that Sen. Strom Thurmond (R-S.C.), who introduced Reagan today, would remain Judiciary Committee chairman, instead of being replaced by "a liberal" such as Sen. Edward M. Kennedy (D-Mass.) or Joseph R. Biden (D-Del.).

Drought is the dominant topic in this state, which has suffered since the spring from a combination of sparse rainfall and record heat. In the invocation today, the Rev. Joseph Roth included a prayer for rain. Reagan said that the drought had reached "tragic proportions" and that the Department of Agriculture was ready to provide emergency assistance.

In a speech concluding a two-day campaign swing, Reagan again sounded the anti-Washington themes that were featured in his speeches Wednesday in Dallas and Miami. The president said that when he left the White House, chief of staff Donald T. Regan said they were "leaving the beltway and going out where the real people are."

South Carolina has been cited by some Reagan advisers as a state in which his intervention could prove crucial. Campbell and lieutenant governor nominee Rep. Thomas F. Hartnett, whom Reagan called the "dream ticket," are in a tight race with Daniel and state Sen. Nick Theodore.