Yes, it's way too early to be prognosticating about the 2016 election. But yes, everyone's already doing it, and if you can't lick 'em....
Anyway, I've been reading quite a bit of material lately about Hillary Clinton's perceived advantages and weaknesses as a presidential candidate. On the advantages side, the Democratic nomination is clearly hers if she wants it (although, yeah, it seemed that way back in 2006, too). Not that it's predictive of much at this early date, but she has an absurdly large 60-point lead over her nearest Democratic opponent in recent polls. Also, the largest liberal Super PAC, Priorities USA Action, has endorsed her possible presidential bid, and former Obama campaign manager Jim Messina will be running those efforts. All this suggests that she is running more or less as the incumbent and that her nomination would be more like an anointment than a contest. (See Jonathan Bernstein for why that's not necessarily a good thing for the Democratic Party.)
As Barack Obama demonstrated, a lack of legislative accomplishments will prevent you neither from becoming president nor from accruing impressive legislative accomplishments once you're there.
And in the general election, she's liable to be a formidable candidate. While few of her speeches are inspiring, they're almost all quite good. She's a smart and skilled debater and reputedly a master in more intimate settings with small numbers of key voters. She's a very capable fundraiser and maintains close ties to the 42nd and 44th presidents, two of the best fundraisers in Democratic Party history. She'd basically have the Obama campaign technological infrastructure handed to her. And she rarely, rarely makes mistakes.
OK, what about her liabilities? This is something Andrew Sullivan and others have been blogging about a bit lately. For one thing, Sullivan points out, Clinton's record of legislative accomplishments is far from impressive. Another problem is that the public may just be tired of her. (I mean, good Lord, we have approval ratings on her going back to 1993, longer than most of my students have been alive.) A third concern is that, well, what exactly is her rationale for running? What would be her signature issue, now that, say, health care reform, for which she advocated from the early '90s to 2008, is now the law?
My reaction to these concerns is that they largely don't matter. (I push back against the Clinton fatigue here.) As Barack Obama demonstrated, a lack of legislative accomplishments will prevent you neither from becoming president nor from accruing impressive legislative accomplishments once you're there. And voters don't really care much about rationale, probably aware that every presidential candidate's true rationale is, "I'd like to be president and I think I'd do a pretty good job." These are mainly issues that political journalists stew over, and not without cause! Writing about the same person in the same way for a quarter century is extremely tedious, particularly when that person is sitting on a large lead and her strategy is to say as few risky things as possible.
But voters, we know from a long line of research (PDF), don't really focus on these things when deciding on their next president. Their main concerns are the status of the economy, the presence or absence of war, and the perceived moderation of the candidates. If the economy is growing reasonably well in 2016, if we are not engaged in a massive bloody war, and if Clinton is not perceived as excessively ideological (relative to her Republican opponent), she'll have a very good shot of winning the general election. A recession that year would likely doom her or any other Democratic presidential candidate. To a modest extent, her campaign skills and organization may make a difference (and there the view is mixed, as she may have both the Obama ground game people and the Mark Penn micro-trends people under the same tent).
But these are the same features that affect any presidential candidate, and they are, to a great extent, out of her control. Yes, she is an unusual candidate—the path from First Lady to Senate to Secretary of State to the Oval Office is not a well-worn one. And being the first female major party nominee surely isn't nothing. But she'd still be subject to the same forces that have made or broken presidential candidates before her, and there's little she can do about that.