President Barack Obama, left, stands with Sen. Hillary Rodham Clinton, D-N.Y., after announcing that she is his choice as Secretary of State during a news conference in Chicago. (AP Photo/Pablo Martinez Monsivais, File)

There's a strain of thought in politics these days -- prominent among Democrats but shared by even some Republicans -- that it's going to be very hard to beat Hillary Clinton in 2016.

Maybe.  Clinton does have many strengths including a long and deep resume and a knack for fundraising. (Not to mention the demographic and electoral college edges that any Democratic nominee will likely carry.)

But, her ascendance to the presidency is anything but a sure thing. There's lots of reasons for that but one of the big ones is that her time spent as Secretary of State for Obama will make it difficult for her to present herself as something new and different to voters almost certainly in the market for something, well, new and different.

A question asked by Quinnipiac University polls in Iowa, Colorado and Virginia this week illustrates that challenge. Asked "Would you like to see the next President generally; continue with Barack Obama's policies or change direction from Barack Obama's policies", just 34 percent of Iowans and Coloradans said they want the next president to move forward on Obama policies while just three in ten (31 percent) of Virginians said the same.

No problem, say Hillary allies. She isn't the same person as Obama -- hard to argue -- and will make her own way. Ok.  That is possible -- especially because Clinton not only ran a long and nasty primary campaign against Obama (thus allowing her to say she isn't an Obama clone) but also because she has been in politics for a very long time and has carved out a political identity entirely apart from Obama.

But, it being possible doesn't mean it's the most likely scenario.  Republicans have, for months, been bashing Clinton as an Obama loyalist and a rubber stamp for some of his more controversial foreign policy decisions. Her time as Secretary of State -- no matter her relatively subtle attempts to distance herself from his decision in, say, Syria -- make it virtually impossible for Clinton to totally beat back the attack that voting for her represents a third term for Obama.

Further complicating Clinton's path to the presidency is that too much distancing from Obama's policies too soon could lead to a rebellion among liberals who remain very committed to Obama and his agenda and already aren't in love with Clinton.  With every day that passes and Elizabeth Warren makes no move toward running (she just isn't going to do it), that concern lessens a bit for Clinton. But, even without a Warren-like figure in the race, beating back discontent from liberals isn't exactly how Clinton and her team want to spend the next six months.

This phenomenon isn't unique to Clinton.  There's a reason that the last time one party won three straight presidential elections was way back in the 1980s -- and that George H.W. Bush lost his bid for a second term in 1992. Eight years later, then Vice President Al Gore never could get comfortable talking about the Clinton years, and lost.  Eight years after that, Barack Obama surged to the presidency by labeling John McCain as a continuation of the George W. Bush's unpopular policies. (Nevermind that McCain had run against Bush eight years earlier in a Republican primary.)

It is possible that if Obama's favorable ratings continue to improve along with perceptions of the economy then attacks against Clinton as an Obama third term might not be so problematic. Of course, Gore's defeat amid high popularity numbers for Clinton suggests that voters may simply like to give the other side control every eight years or so -- almost regardless of their views on the state of the country.

Clinton (still) isn't an official candidate as she and her team spend these months strategizing on the race to come.  One of the key questions she needs to find an answer for is how to cast herself as both supportive of the direction Obama has taken the country while simultaneously committed to leading it in her own new and different direction.

That's a tough one -- and proof of why the idea of a Clinton coronation in 2016 is far-fetched.