Hillary Clinton: What's her 2016 plan?

"Everyone has a plan until they get punched in the mouth."

It's a quote from boxer Mike Tyson that has become a favourite of political players in the US.

Thanks to the growing controversy arising from her use of private email during her time as secretary of state, Hillary Clinton's presidential plans are disappearing in a flurry of punches. A controlled launch of her campaign in July is on the scrap heap, and an April announcement - on the heels of press conferences and damage control - seems more likely.

Now critics on the right and the left are landing blows that can't be easily dismissed - amounting to a rather abrupt reversal of fortune.

Just a few weeks ago, Mrs Clinton appeared to be riding high. She had built up considerable goodwill over the last six years. While her primary against Mr Obama was contentious, she played the good soldier after conceding defeat.

She worked to help Mr Obama win in 2008 and served as his secretary of state for four years. In 2012, when the president was in desperate need of a boost during the Democratic National Convention, it was her husband who made the most compelling case for his re-election with a prime-time speech.

On a personal level, Mrs Clinton also appeared strong. Her time as secretary of state gave her a political gravitas she didn't have as first lady or even as junior senator from New York. Her popularity in opinion polls soared, and photos of her using her Blackberry became a good-humoured internet meme.

The email controversy, however, threatens all that.

It's most dangerous to her because it risks turning what was one of her strongest assets - her time as secretary of state - into a weakness. Even the Blackberry meme now has a darker hue.

The controversy reminds many people not of the new Hillary Clinton, who had become a well-liked, glass-ceiling-cracking public figure, but of the defensive, "vast right-wing conspiracy" touting political player.

David Corn says Mrs Clinton relies on a "combative' communications strategy stuck in the 1990s

David Corn of Mother Jones, recently the target of conservative ire for his expose on Fox News host Bill O'Reilly, hammers this point in a recent column.

"The Clinton camp's handling of the controversy was a sign that Hillary and her gang are stuck in the Whitewaterish 1990s when it comes to communications strategy, relying on always-be-combating tactics predicated on self-perceived persecution," he writes. "It's bad news for anyone hoping that Hillary 2016 has learned from the miscalculations of the past."

As secretary of state she should have been more considered, he writes, more careful given her political ambitions.

"For decades, she has seen what happens when a Clinton slips up," he writes. "Fair or not, with this power couple, the volume knob does go up to 11. If not 12."

And so the response from her team so far has been aggressive and not humble, confrontational and not conciliatory - which only aggravates the situation. Blanket denials, no matter the evidence, lead to blanket disbelief.

What's more, even as Mrs Clinton addresses the issue in her press conference on Tuesday, the controversy likely won't go away - and could easily metastasise into something much more serious.

New York magazine's Jonathan Chait draws a comparison to the most prominent 1990s Clinton scandal.

"The Clinton impeachment ultimately grew out of a spiralling investigation that began by poking into Whitewater, which turned out to be a non-scandal," he writes. "The Clinton email disclosures grew out of the investigation of Benghazi, which was also a non-scandal that likewise survives only in conservative fever dreams. Investigations that pry into internal correspondence, even those based on a groundless suspicion, can eventually yield, or create, meta-scandals of their own."

Maybe Hillary Clinton was always destined for some kind of decline. Maybe the sense of inevitability, the buoyant poll numbers and the lack of credible opposition for the 2016 Democratic presidential nomination were an artificial high, and a reckoning was inevitable.

It's certainly true that the media love for building possible political candidates up is matched only by their apparent glee in knocking them down. It makes for good copy.

But this is Mrs Clinton's first test in the 2016 campaign. And how she handles early tests like this could go on to define her entire candidacy.

"A penchant for control and secrecy," writes Politico's Roger Simon - another prominent voice on the left. "That is not exactly the campaign slogan Hillary has been looking for."

Up until recently it looked like Mrs Clinton would have an easy path to the Democratic nomination and emerge from the process politically unscathed and ready for the general election. While the former may still happen, the latter is appearing less likely.