If you listen to the chattering class in Washington, D.C., Hillary Clinton is a virtual certainty for the 2016 Democratic nomination, and the front-runner in the next presidential race.

But in private, rumors persist that the former Secretary of State may not even be capable of making it to Iowa and New Hampshire. Clinton, these skeptics often say, will not run for president again because of health concerns.

These ubiquitous rumors of her health have been fueled in part by the supermarket tabloids. The National Enquirer wrote in 2012 that Clinton had brain cancer, something a spokesman dismissed then as “absolute nonsense.” In January of this year, the Globe claimed that Clinton secretly had a brain tumor.

Asked about her health on Thursday, Clinton spokesman Nick Merrill said in an email to The Daily Caller: “To your question, very caring of you to ask. She’s 100%.”

But the rumors suggesting otherwise date back to the end of 2012, when Clinton’s health made headlines as she finished her term as secretary of state: aides explained then that she developed a stomach virus, hit her head, suffered a concussion and subsequently developed a blood clot in her brain but was being medicated and was expected to recover. (TheDC TV: Could Clinton be hurting the Democratic Party?)

But skeptics say there is much more to the story of her health, which has recently been the subject of increased speculation in Washington.

Because of these rumors, some on the right have been convincing themselves that Hillary is sick and therefore won’t run — a bombshell that would upend the 2016 race.

Roger Stone, a GOP consultant, wrote on Twitter recently that Clinton is “not running for health reasons,” telling followers to “remember you heard it first” from him.

Conservatives aren’t the only ones skeptical about whether Clinton has been open about her health. At the time of Clinton’s hospitalization in 2013, Melinda Henneberger of the Washington Post wrote a piece titled, “How sick is Hillary Clinton?”

“Already,” Henneberger wrote, “reports that describe Clinton’s right transverse sinus venous thrombosis as potentially life-threatening, though apparently caught in enough time, sound a lot more serious than the word from her doctors that the secretary is ‘making excellent progress and we are confident she will make a full recovery. She is in good spirits, engaging with her doctors, her family and her staff.'”

Henneberger asked then if we would “really be shocked to learn down the road that reports during her hospitalization had put a positive spin on her condition?”

“Our public officials have trained us to take everything they say with a healthy dose of skepticism,” Henneberger continued, “and on a matter as sensitive as a head injury followed by denials of any neurological symptoms, I’m not sure why we would or should unquestioningly accept the word of any politician.”

Some have noted Clinton’s change in appearance, including the addition of thick glasses, since her hospitalization. “One doesn’t need to be a physician… to have seen that Clinton has not appeared exactly bright-eyed and bushy-tailed of late,” Mary Stanik, a former Minnesota health care spokeswoman, wrote in 2013. “She looks to have gained a significant amount of weight since 2008. She seems pale, tired, and yes, aged. She’s said that she would like to know again what it’s like to not be tired.”

Last year, a Clinton aide acknowledged that her health crisis caused her to stop wearing contact lenses.

“She’ll be wearing these glasses instead of her contacts for a period of time because of lingering issues stemming from her concussion,” spokesman Philippe Reines told ABC News in 2013. “With them on, she sees just fine.”

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