If nothing else, the Republican Party is a perpetual irony producing machine. Karl Rove, a man nicknamed "Bush's Brain" for guiding an alcoholic to two terms in the White House, suggested 2016 Democratic frontrunner Hilary Clinton suffered brain damage as a result of a December 2012 fall. Rove, who now contends a concussion could be a disqualifying event despite having pulled the strings for a man who knocked himself out after choking on a pretzel, has company among the GOP's leadership. On Sunday, RNC chairman Reince Priebus declared Clinton's age and health are "fair game."
Those are pretty amazing claims for any conservative to make. After all, three of the GOP's last six presidential candidates--Ronald Reagan, Bob Dole and John McCain--were or would have been older on their first inauguration day than President Hillary Clinton would be on January 20, 2017.
Ronald Reagan was within days of his 70th birthday when he took the oath of office in 1981. Whether or not he was already suffering from Alzheimer's symptoms during his tenure in the Oval Office, as his sons Ron and Michael would later heatedly debate, his aides and allies were clearly concerned. As Margaret Thatcher famously described the Gipper, "Poor dear, there's nothing between his ears." Regardless, after his catastrophic performance in his first debate against Walter Mondale in 1984, Reagan rebounded with classic formulation:

"I will not make age an issue in this campaign. I will not exploit, for political purposes, my opponent's youth and inexperience."

In 1996, it was 73 year old Kansas Senator Bob Dole who carried the GOP banner against President Bill Clinton. And it was Hillary's husband who put to rest any question of Dole's age during an October 1996 debate:

"I can only tell you that I don't think Senator Dole is too old to be president. It's the age of his ideas that I question."

As early as 2006, John McCain was launching preemptive strikes against the age issue. Like Reagan, the 72 year old former POW and war hero turned to humor. As he told a group of Republican governors at a gathering in in Florida, "I am older than dirt. More scars than Frankenstein." At turned out, it didn't help matters when the Maverick bungled his own punchline, as he did in front an MTV audience in December 2007:

"I'm older than Frankenstein. I gotta few scars. I'm older than dirt and I've got more scars than Frankenstein...Screwed up that line."

Of course, McCain needn't have worried about any blowback. After all, he wasn't a Democrat. Like Hillary Clinton.