In 2008, Hillary Clinton was running against an inexperienced, untested young senator named Barack Obama. Clinton was known as one of the most serious policy wonks to ever run for president, and her network included most of the Democratic Party's top policy staff, many of whom had worked directly for her or her husband.

But somehow, much of the Democratic policy establishment ended up supporting Obama. No one doubted that Clinton knew policy inside and out; they doubted that she would make the right calls in the face of public pressure.

The Iraq War loomed largest here, but a smaller, though still important moment was when Hillary Clinton proposed suspending the federal gas tax for the summer travel season. Economists hate this sort of policy pander: It encourages people to use more gas, robs the highway trust fund of revenue that needs to be raised some other way, and ends up raising gas prices because of increased demand.

But it polls well. And Clinton, who knows better, signed on to it. So did John McCain. But Obama didn't. He slammed the proposal as "short-term, quick-fix" thinking, and said, "This isn't an idea designed to get you through the summer, it's an idea designed to get them through an election."

Policy wonks agreed, and Clinton faced a storm of criticism for her pander. She was reduced to protesting, "I’m not going to put my lot in with economists," which didn't endear her to economists — or to anyone who actually does want policymakers to listen to economists when designing tax policy.

Obama had his struggles with policy opportunism, too — notably, when he left the individual mandate out of his health-care plan, which led to a lot of health policy experts preferring Clinton (Obama ultimately flip-flopped on the issue in office). But it was moments like the Iraq War and the gas tax that helped Obama win over much of a Democratic policy establishment that had no reason to trust him.

Clinton keeps taking positions that are ... hard to believe

Of late, Clinton is again looking like the kind of candidate who puts polls in front of policy.

First, she came out against Obamacare's Cadillac tax — a policy that enjoys wide support among health economists. Clinton knows the problems of the massive deduction for employer-provided health insurance well; decades ago, her health-care plan wiped out the tax code's preference for employer-based health care, and in 2008 she had a smaller, more targeted, version of the Cadillac tax in her proposal.

I want to be clear here. Lots of people oppose the Cadillac tax, and for lots of reasons. What I have trouble believing is that Clinton and her policy advisers really think the Cadillac tax is a bad idea. Her past policies embrace its theory, her past advisers helped pass it into law, and virtually everyone who spends their days thinking about how to control health-care costs considers it one of Obamacare's most promising provisions.

On Wednesday, Clinton came out against the Trans-Pacific Partnership trade deal, saying that she's concerned with the provisions around pharmaceuticals and the absence of provisions around currency manipulation. But as Tim Lee notes, Clinton strongly supported early versions of the deal — she called the TPP "the gold standard in trade agreements" — that were worse on pharmaceuticals and identical on currency manipulation.

Good grief, the architect of "the pivot to Asia" opposes TPP? In her book she praised the deal! pic.twitter.com/9XDiv0btzM — Ryan Lizza (@RyanLizza) October 7, 2015

Again, the argument here isn't that there aren't reasons to oppose the TPP, but rather that knowing Clinton's record, her advisers, and her past comments about the deal, it's hard to believe Clinton really opposes the TPP deal.

Something of the same could be said for the Keystone XL pipeline. Clinton's initial take on the pipeline was positive, and then she said she wouldn't take a position until she was president, and then she finally came out against it. I'm a bit more inclined here to credit Clinton's position as authentic — she's a climate hawk, and while my sense is she thinks both sides make too big a deal over Keystone, I can see her leaning against it — but it's not exactly a bold, polls-be-damned approach to the issue.

Opposing these policies may not even be good politics

Clinton's reputation as a policy wonk is sterling; it's common to talk to Democratic (and, in some cases, Republican) staffers who tell you that they've never briefed a politician as sharp and informed as she is.

But Clinton's reputation as a policymaker is iffier — her critics can rattle off a long list of important decisions, ranging from the Iraq War to the bankruptcy bill, where they think she was swayed by polls or interest groups.

Clinton, of course, isn't just a policymaker — she's a politician, and particularly when it comes to reading polls and managing interest groups, she's a good one. Her vulnerability in the Democratic primary comes from the left, and to keep liberal challengers from gaining support, she needs to hold union support. Coming out against the TPP and the Cadillac tax is a great way to win over unions.

But it's not a great way for Clinton to show she's willing to make some unpopular decisions if they lead to better policy — and that has political benefits that don't show up in narrow issue polls.

I don't truly know what's in Clinton's heart — perhaps I'm wrong, and despite all evidence to the contrary, she holds all these positions deeply — but as a close reader of her record, I'm not convinced that Clinton, in office, wouldn't support policies like the Cadillac tax or negotiate trade deals like the TPP. And as someone trying to understand Clinton's likely governing philosophy, it's unnerving.

And this is a broader problem for Clinton. Her political weakness, fairly or not, is that the voters and the media — or maybe it's the media and, thus, the voters — have decided that she's unusually poll-tested and calculating, even for a politician. Politically convenient policy changes don't help, and they cut against what should be her greatest asset: that she's an extraordinary policy mind who understands these issues better than her challengers, and so can be trusted to make better decisions on them.

For more thoughts on Hillary Clinton's 2016 presidential campaign check out Vox's new podcast, "The Weeds" featuring Ezra Klein, Matthew Yglesias and Sarah Kliff. You can listen on Soundcloud and subscribe to new episodes on iTunes.