I have no clue whether or not Hillary Clinton will run for the presidency in 2016, but I would argue that she would be the strongest nonincumbent frontrunner in modern history upon inspection of the primary landscape.
1. Clinton's polling at a record 61% in the early primary field
You might wonder how normal that is? It's in another stratosphere. I went into the Roper archives to examine races where no incumbent was running for re-election, and only Al Gore, at around 55% in early 1997 for the 2000 run, comes anywhere close. George HW Bush was only around 40% at this point in the 1988 cycle; Bob Dole was near 50% for 1996; and George W Bush was between 20% and 25% in 2000.
Some might be tempted to say that Clinton is only where she is at because she's holding a high-end nonpartisan position (secretary of State). Colin Powell, a candidate who also held a high-end nonpartisan position, was in the mid 20s at this point for a 1996 run, and mid 30s for 2000. Clinton is also polling well above her 2008 numbers at this point in the campaign. Back in late 2004 and early 2005, Clinton was in the mid 30s to low 40s.
Some may be quick to dismiss early survey data, but almost always, those like Dole, Gore and now Clinton, who poll high this early and run, tend to march to the nomination.
2. Clinton is on her way to winning the endorsement primary
More important than even polling is whether the party establishment backs you. Remember how no one in the grassroots seemed to like Mitt Romney during the primary season? Folk like me thought he was going to win because most primary voters eventually take their cues from party leaders. If a candidate clearly wins the "invisible primary" (like Reagan in 1980, Mondale in 1984, Bush in 1988, Clinton in 1992, Dole in 1996, etc), then they're almost certainly going to win the nomination.
In 2008, Hillary Clinton failed to overwhelmingly win the invisible primary, even if she had the most endorsements. Both Senate majority leader Harry Reid and then-speaker of the House Nancy Pelosi were looking for an alternative.
Clinton's likely not to have those same issues in 2016. In addition to holding on to her support from 2008, Clinton already has the backing of Nancy Pelosi.
President Obama isn't likely to get in her way, either. He felt such a debt of gratitude to Bill Clinton that he was the first person Obama called after Mitt Romney conceded the 2012 election. Obama continues to play golf with Clinton to this day. Obama and Hillary's working relationship is also solid.
3. Clinton has organization in the early primary states
One of the reasons that Clinton lost in 2008 was due to her loses in key early primary states, Iowa and South Carolina. Obama's campaign simply out-planned Clinton's and had organizations that hers was catching up to.
Take the first-in-the-nation Iowa caucus (and its complicated rules): you need to be able to organize. You need a good get-out-the-vote effort and the ability to win the eventual support from voters whose first candidate doesn't reach the 15% threshold. Obama had it, and Clinton didn't recognize that until it was too late.
This campaign-building has to be done from scratch for most candidates. Clinton already has a foothold in all early primary states, and the later states as well, because of the drawn-out 2008 primary season. That advantage simply can't be understated.
4. Clinton isn't going to make an idiotic statement
A lot of candidates with a lot of promise enter the race with high polling numbers yet fail miserably as candidates. Rick Perry most recently entered the 2012 Republican race with solid polling numbers and much media hoopla. Unfortunately for Perry, he had to open his mouth. Ted Kennedy suffered a similar fate in 1980.
Clinton is no rookie. Anyone who watched the 2008 debates will tell you that, despite having been in the line of fire throughout the 2008 primary, Clinton never made a statement that ruined her candidacy. In fact, outside of one comment about undocumented immigrants and drivers' licenses at a late October 2007 debate, Clinton was a top debater during the 2008 primary season.
5. Clinton's got the demographics on her side
Finally, primaries are about putting together voter coalitions. In 2012, Mitt Romney discovered there were slightly more non-evangelicals than evangelicals voting in Republican primaries. In 2008, Barack Obama won on the strength of African Americans, college-educated whites and young voters. His coalition was just slightly larger than Clinton's Latinos, non-college-educated whites and women.
The Clinton name is still gold among non-college-educated white Democrats, as witnessed by Obama's deployment of Bill Clinton to win over these voters in 2012. There's not going to be a Latino in the primary field, so one would think Clinton's previous support will hold. There still hasn't been a woman president, and there's unlikely to be another female running, so Clinton will retain her 2008 levels among women, as well.
Perhaps most importantly, there's not going to be African-American opposition on the same level as Obama. Clinton had been expected to do very well among black voters, even after Barack Obama entered the race. Right now, her support among black Democrats is on par with her support among white Democrats. Even if Clinton only takes 20% to 30% of the black vote, it'll be more than enough to win.
And we haven't even talked about the fact that the Clintons can raise a lot of money.
The fact is, if Clinton runs, she'll be a heavy favorite.