The Republican disadvantage on the air in recent news is starkest in Michigan and Kansas. Voters say what they’ve learned over the last few weeks has made them think worse of Terri Lynn Land, the Republican, by a 22-point margin, compared with a five-point drop in their view of the Democrat, Gary Peters. Similarly, 32 percent of likely voters say recent advertisements have pushed them toward Mr. Peters, compared with 26 percent saying that of Ms. Land.

In Kansas, voters by a margin of 32 to 25 say they’re more likely to support Greg Orman, the independent candidate, as a result of ads. Mr. Orman had the advertising airwaves to himself for months, a streak that came to an end only in the middle of September.

Mr. Orman is the only candidate whom voters say they feel more favorably toward as a result of what they’ve heard over the last few weeks, though by only a two-point margin.

Voters also say recent news has made them feel worse about Republican candidates than Democratic ones in North Carolina and Georgia, albeit by more modest margins than the Republican disadvantage in Michigan and Kansas.