The same pattern of partisan differences over the importance of candidate age occurred in 1996 when Bob Dole was the Republican presidential nominee. A July 1996 CBS/New York Times poll found that 48 percent of Democrats thought Mr. Dole’s age (he would have been 73 upon taking office) was an obstacle to him being an effective president compared with 37 percent of independents and 17 percent of Republicans. And before Mr. Dole, it was Ronald Reagan (age 69 at his first inauguration) who Democrats suggested might be too old to be president.

With the 2016 presidential election looming, however, it is Democrats who appear likely to be supporting an older presidential candidate. Hillary Clinton would be 69 years old if she took office and would presumably face a younger Republican candidate if she won the Democratic nomination.

As expected, Democrats are now starting to feel more positively toward older candidates: The new Pew poll found that only 44 percent said they would be less likely to support a presidential candidate who is 70 or above, a decrease of 16 percentage points from the 2007 poll — a drop that Pew called “particularly notable” relative to the smaller decreases observed among Republicans (from 42 percent to 32 percent) and independents (from 43 percent to 34 percent).