On Clinton's age, Republican rivals imply -- but never say -- she's old

“It’s unwise to attack a political opponent based on her immutable characteristics, like race, gender and age,” said Republican pollster Kellyanne Conway. She said she has met with at least five Republican presidential campaigns seeking her services and none of them has indicated they want to go after Clinton on issues involving her age.

With Clinton swamped by questions about foreign donations to the Clinton Foundation and criticism of her use of a private email server while at the State Department, there is also simply no reason at the moment to engage in an attack that could be more divisive than beneficial, Republican strategists said.

They fear that highlighting Clinton’s age could alienate women voters whom Republicans need to be competitive in next year’s general election.

Democratic pollster Anna Greenberg said women older than 50 would likely comprise the largest bloc of voters in 2016.