DES MOINES, SEPT. 23 -- Even before the first caller had a chance to question Vice President Bush on the hour-long live WHO radio program this morning, the vice president reeled off the names of European leaders he plans to meet next week.

"I'm off on a trip to talk to our NATO allies -- Margaret Thatcher, Helmut Kohl, Francois Mitterrand," Bush said as he opened the conversation with WHO radio host Kevin Teale, which was broadcast to about 200,000 listeners.

Bush mentioned Thatcher by name several more times during the show, in a scene that was a vivid reminder of the two hats Bush is wearing as he struggles to fend off intensified challenges from other Republican candidates for the presidential nomination.

One is the "statesman" role of an experienced diplomatic trouble-shooter who plans to leave Thursday for a 10-day European tour -- including a visit to Poland, reflecting the recent improvement in relations between the United States and the communist regime there. Bush aides say this is an "official" mission, but the vice president has hired a campaign video crew to record scenes in Poland and Western Europe for use as political commercials.

Bush's other hat is that of a troubled front-runner who has suffered early setbacks and who returned to Iowa today with a busy schedule to demonstrate that he can still campaign within close range of Iowa's caucus voters. George Wittgraf, Bush's Iowa chairman, said there is a "lingering perception that the trappings of the vice presidency are keeping him from being in touch with Iowa Republicans."

Bush wanted to "get out from behind the podium," Wittgraf said. After his embarrassing third-place finish in a straw poll Sept. 12, Bush scheduled a quick return today that included the WHO appearance; lunch with Iowa reporters; jogging with the cross-country team at Dowling High School, a large Catholic school; a strategy meeting with Iowa backers; observance of Rosh Hashanah, the beginning of the Jewish New Year, at a private residence; a basketball-shooting, picture-taking session with a 10-year-old athlete, and attendance at a block party in a heavily Republican Des Moines precinct. Bush is planning more Iowa visits after he returns from Europe, aides said.

The straw poll defeat was "like getting a good swift kick in the tail in the exhibition game before the season starts, and they've unleashed a tiger now," Bush said. "We are going to work like we've never been heard from in this state. So take a couple on the chops -- clean up your act after exhibition season and win in regular season."

Bush tried repeatedly today to translate his foreign policy experience into political advantage, saying, for example, that the agreement in principle with the Soviets on a treaty to eliminate medium- and shorter-range missiles is "good foreign policy" and "a good issue for me."

But the vice president today also volunteered a new explanation of the origins of the Iran arms sales that was at odds with his earlier statements. Bush and President Reagan have said the arms sales initially were an effort to reach out to moderate factions in Iran, not a deal for the hostages.

Bush said today: "You're familiar with the Iran-contra thing, where a plan to try to release the hostages turned out to be hostages for arms, which we opposed."

Bush noted that he was chairman of a task force on terrorism, which emphasized in its report that the United States would not make concessions to terrorists. However, Bush did not discuss his participation in meetings on -- and his apparent assent to -- Reagan's decision to sell weapons to Iran.

The vice president's trip to Europe is designed in part to restore luster to his foreign policy credentials just before his planned Oct. 12 formal announcement of candidacy. He is the highest-ranking U.S. official to visit Poland since President Jimmy Carter in 1977. Although Bush supported the U.S. economic sanctions against Poland after declaration of martial law in December 1981, he plans to recognize recent liberalization measures and an improvement in relations. Aides said the trip may result in the announcement that both countries will restore their ambassadors, but Bush is not carrying concessions to Poland on international economic matters. He plans to meet with Polish leaders, with Solidarity union leader Lech Walesa and with church leaders. He has also been given permission for a five-minute television broadcast.

Bush said his foreign policy duties are "not just show business" and defended plans to use a campaign camera crew in Europe on grounds that Senate Minority Leader Robert J. Dole (R-Kan.), a rival in the race, had one in Nicaragua and that Reagan had taken one to Normandy.

Acknowledging that his overall views have come across as "hazy" to voters, Bush promised today to "clarify" his positions. But his responses to some questions on domestic policy also underscored the conflicts Bush faces as he attempts to emerge from Reagan's shadow.

For example, Bush acknowledged that the administration had never submitted a balanced budget, then blamed deficits on Congress, saying, "Congress appropriates every single dime . . . . Congress is a major part of the problem . . . . I blame the Congress for taxes, I blame the Congress for deficits." Bush said that if he were elected, the earliest he would balance the budget would be in five years.

Asked if he would be willing to eliminate farm subsidies, which have reached a record $26 billion a year under the Reagan administration, Bush said, "I'd like to see it phased out as quickly as can be." But he added, "We're not going to leave these farmers that are hurting in the lurch overnight." He then said he supports Reagan's 10-year phase-out, but only if U.S. allies also reduce subsidies and trade barriers.

Bush said today he has come to feel "inhibited" by the trappings of the vice presidency, but his aides are clearly hoping to use his "stature advantage," as some have called it, to best advantage. Sources said Bush is considering an official trip to the Far East before the Iowa caucuses in February.