To the surprise of no one, the Nielsen overnight figures indicate that ABC's decision to postpone until last night its broadcast of the Democratic response to President Reagan's State of the Union address paid off.

In the nine major Nielsen markets, Wednesday night's episode of "Dynasty" averaged a 27.6 rating and a 43 share, with a 28.2/48 on WJLA (Channel 7) here. That means that 28.2 percent of all TV sets and 48 percent of the TV sets in use in the Washington market were tuned to the trials and tribulations of the Carrington clan.

Since "Dynasty" aired at different times in different time zones, there is no direct comparison of the three networks' ratings in the nine major markets. However, in the Washington market, where "Dynasty" aired from 10 to 11 p.m., WDVM's broadcast of the Democratic response, news analysis and "Alice" managed a meager 5.7 rating and a 9 share; WRC received the same rating and share for its broadcast of the Democratic response and analysis.

The decision by ABC, currently in last place in the 1984-85 regular-season ratings race, to air "Dynasty" instead of the Democratic response comes during the February ratings sweeps. February is one of four months during the year when ratings are used to determine the advertising rates of local affiliates. Although "Dynasty" appears to have dominated the time period during which it aired, the national Nielsen figures (which include rural areas) have not yet been tabulated.