Washington — Democratic officials are bracing themselves for an ``October surprise'' -- possibly a Soviet grain deal -- to bolster Republican campaign prospects for the Congress. Rep. Tony Coelho of California, chairman of the Democratic Congressional Campaign Committee, says he doubts that President Reagan would have agreed to this weekend's summit in Iceland unless he were sure the meeting would be a political plus.
Both Republican and Democratic strategists say that the GOP's greatest problems in House and Senate races this fall are in the Midwestern farm belt.
Overall, Democrats are expected to pick up about 10 to 15 House seats, many of them in the Midwest. Democratic prospects have also been brightening in Senate races in North Dakota, South Dakota, Wisconsin, and Missouri. Mr. Coelho told reporters at a breakfast meeting on Thursday that, to be effective, a grain pact must be a multi-year deal that would get America's farm export pipeline flowing again.
Democrats clearly are concerned about the possible political impact of the summit, which comes only three weeks before Election Day. A major breakthrough on agricultural trade, arms -- or both -- could threaten Democrats' hopes for taking over the Senate and enlarging their control of the House, where they now enjoy a 253-to-182 margin.
Coelho, by raising the prospect of a grain deal with the Soviets, may be ``setting up'' the President for criticism if Mr. Reagan comes away empty-handed from his meeting with Soviet leader Mikhail S. Gorbachev.
Coelho claims that, during the past three weeks, Democratic prospects have improved in races for the House. The principal reason, according to Democratic polls and consultants, appears to be growing concern about the US economy.
Democrats hope to exploit discontent over a number of economic issues: the recent uptick in unemployment (to 7 percent); depression in the Midwest farm belt and the oil patch states of Texas, Oklahoma, and Louisiana; the stagnant stock market; the fact that as many as 31 states are not sharing in current prosperity; and the twin deficits on trade and the federal budget.
``We have to do everything we can to put the focus where it belongs -- on the economy,'' says Coelho.
But there is concern among Democrats that the next week will be lost to their campaign because of the national focus on presidential summitry. Recent momentum gained by the Democrats could vanish.
Democratic claims that unease over the economy could help their cause in November are supported by a recent poll by the Washington Post and ABC News. While concern about the economy isn't as severe as in 1982, during a serious recession, the Post-ABC poll found that more people now feel the economy is getting worse (35 percent) than better (27 percent). However, the Post-ABC analysis found that so far this hasn't hurt the GOP badly.
The poll indicates Democratic gains in the House of only three to eight seats. If the Reagan-Gorbachev summit helps Republicans hold their losses to that level, that result will be seen as a major Democratic setback.