The results reaffirm the tradition that voters in midterm elections typically skew older, the Princeton, N.J., polling agency said.
The Gallup Daily tracking results also underscore the need for President Barack Obama and fellow Democrats to rally the voting segment that helped propel Obama into the White House, the pollster said.
Younger voters offer a good news-bad news scenario for Democratic candidates in recent elections, Gallup said. The positive that younger voters disproportionately are drawn to Democratic candidates is tempered by the negative that younger voters have a history of staying home on Election Day.
Results are based on nationwide telephone interviews 5,490 adults conducted April 1-25 as part of Gallup Daily tracking. The margin of error is 1 percentage point.