We spend an awful lot of time in campaigns talking about a set of personal qualities candidates may or may not possess that revolve around honesty. Is the candidate truthful, honest, sincere, candid, authentic? The New York Times asked yesterday whether Hillary Clinton's focus on inequality was sincere: "the former secretary of state must persuade voters that she is the right messenger for the cause of inequality, not simply seizing on it out of political expedience." My colleague Greg Sargent argued that if it represents a change in emphasis for Clinton, it's only because her party's agenda has evolved, and that's what the process is for. Matt Yglesias said that it's absurd to think that anyone who understands and agrees with Clinton on the issue of inequality isn't going to vote for her because she's been talking about it more lately than she used to. Jonathan Bernstein agreed, but argued that sincerity could matter for primary voters:
The primary campaign is a different story. A voter who agrees with a candidate's positions down the line may defect to another contender who is more convincing as a true believer. Nominations often involve candidates who seem identical. Can you tell Scott Walker from Marco Rubio from Bobby Jindal from Rick Perry based only on what they've said about where they stand on the issues?
Primary voters as well as the party actors who are involved in a campaign's earlier stages need to find a way to choose. They might see experience as the best indicator of who might be the most effective president. Or they might use ethnicity, gender or other demographic traits as a guide, or something to identify with the candidate personally. They might be drawn to the best speaker or debater, either because they are inspired or because they assume those skills will produce the strongest general-election candidate.
So it wouldn't be unlikely if primary voters look for the candidate who is most likely to stick to his or her promises and discount promises that seem targeted for transient electoral appeal.
I agree that some number of voters will make their choice this way, but I'd argue that doing so is foolish. As we know well, presidents tend to keep the vast majority of the promises they make while campaigning, and most of those they don't keep are merely the ones they tried and failed to do. The actual number of broken promises, a la "Read my lips: no new taxes" is incredibly small. If a candidate says he's going to do something, he's probably going to at least try to do it. This is particularly true when the thing he's proposing is of vital importance to his party. And it's true even if it was something he wasn't all that enthusiastic about, but adopted out of political opportunism.
That isn't to say that sincerity is completely irrelevant—a president will pursue some goals with more zeal than others depending on what he or she cares most about—but if primary voters have managed to extract a promise from every candidate to do something, they can probably consider their work on that issue done, and base their decision on something else. For instance, every Republican is going to say he wants to cut taxes. If you're a Republican, should you waste your time figuring out which of them is more deeply, emotionally, fundamentally committed to cutting taxes? Probably not. The next Republican president, no matter who he is, will try to get a tax-cutting plan through Congress. You'd do better to figure out who has the best shot of winning the White House and who might have the skill to guide that tax-cut plan into law. You don't need a president who's sincere, you just need one who'll do the things you want.