Eric Thayer / Reuters

Senator Elizabeth Warren last week released her Medicare for All plan. This complicated proposal is already drawing scrutiny. Attacks have come, predictably, from conservatives who don’t share Warren’s values and from more moderate Democratic rivals such as former Vice President Joe Biden and South Bend, Indiana, Mayor Pete Buttigieg. Independent observers have also raised questions. A major policy proposal by a leading candidate is, of course, bound to spark debate. Yet beyond the merits of Warren’s plan—about which I have no special insight—was the senator politically wise to get into so much detail?

Politicians have long found value in vagueness. In the 19th century, parties often nominated generals for president. Beyond the respect that battlefield success had won them, military men were attractive to party leaders because they had no political records. Lacking the baggage of past policy stands, generals could potentially appeal to all segments of the voting population by saying as little as possible. The advantages of ambiguity were not limited to military men. In 1916, Republicans looking to heal the disastrous rift between progressive backers of Theodore Roosevelt and conservative supporters of William Howard Taft, which had led to defeat four years earlier, drafted Charles Evans Hughes off the Supreme Court, where Hughes, a former governor of New York, had sat out the Taft-Roosevelt fight while maintaining a judicial and judicious silence about political controversy.

Decades ago, the political scientist Donald Stokes drew a key distinction between “valence” and “position” issues. Valence issues attract broad or universal agreement, whereas position issues prompt division. All voters want a good economy and prefer both peace and victory to messy, protracted war—these are valence issues. People may not agree on how to achieve peace and prosperity, however—these are position issues.

Although incumbents have no choice but to reveal their positions, or policies, canny challengers promise a desirable outcome while saying as little as possible about how they’ll realize it. In 1952, the prolonged stalemate of the Korean War was a political disaster for President Harry Truman and the Democrats. Some sought to escalate the war, going all out for victory. Others wanted to withdraw from a conflict that they saw as peripheral to American interests. Dwight Eisenhower, the GOP’s presidential candidate, straddled this divide by remaining suitably vague. He vowed only that he would go to Korea. Sixteen years later, Eisenhower’s former vice president—Richard Nixon, long seen as a hawk—was able to create the impression that he had a “secret plan” to end the Vietnam War. This plan did not exist, but the notion that Nixon had something up his sleeve appealed to people tired of the war. Ronald Reagan’s 1980 debate question, “Are you better off than you were four years ago?” and Bill Clinton’s famous 1992 slogan,“It’s the economy, stupid,” also reflected a strategic decision to tap into voters’ dissatisfaction with conditions, rather than propose remedies. In 2006, Democrats could not agree on what to do about the Iraq War, only that it had been a mistaken policy poorly implemented by President George W. Bush. That was enough to bring them victory in the midterm elections.

More recent studies suggest that vagueness has value. In a 2009 article, the political scientists Michael Tomz and Robert Van Houweling showed via a lab experiment that participants did not punish and sometimes even rewarded candidates who remained relatively ambiguous on policy.

The value of vagueness might seem especially clear on a policy like Medicare for All, which is not popular with the public as a whole and—with only 14 co-sponsors, including Warren—stands little chance of becoming law in anything close to the form the senator from Massachusetts proposes.

Yet if vagueness has its virtues, Warren had little choice but to release a detailed health-care plan. Start with the fact that her political brand is “I have a plan for that.” She entered politics with a reputation for mastery of detail. She leveraged this wonkish image by releasing plan after plan, generating favorable news coverage that helped her rise from a low poll standing this spring and summer to a top-three candidate. She polls best among highly educated voters who are most attentive to policy discussion.

Moreover, the senator’s previous squishiness on health-care reform, and specifically on whether Medicare for All would require middle-class tax increases, made her seem evasive. Perhaps that’s why a recent ABC/Washington Post poll that otherwise had good news for Warren already found respondents putting her in third place as “most honest” after Senator Bernie Sanders and former Vice President Joe Biden.

Had Warren been the overwhelming favorite for the nomination the way Hillary Clinton was four years earlier, she might have been able to remain constructively imprecise on health care, focusing on goals more than methods and avoiding awkward commitments. But this was not her lot, and having made the strategic decision to compete with Sanders for progressive votes, she had to compete in detail.

Setting aside the particulars of Warren’s situation, structural changes in the nominating process have pushed candidates in the direction of position issues. The 19th-century generals turned candidates, like civilian nominees in that era, got through whole elections without debating or, in many cases, even speaking publicly. As late as 1968, Nixon could win a nomination and general election without a single debate. After that election, reforms in the nominating process led to a great increase in primaries and, eventually, pre-primary debates—each one an opportunity for rivals and journalists to demand specifics. In this cycle, Warren faces three more debates before the first votes are even cast.

Beyond the growth in primaries and debates, the rise of social media has meant that more party activists and primary voters are part of a never-ending conversation about the candidates’ every move in a way that was not true even in the early 2000s. Clips from debates, forums, and speeches are constantly circulated. These hyper-involved voters have distinctive views, and they want to know whether the candidates share them. They won’t settle for promises about outcome; they want to know how the candidate will achieve the outcome. As a result, there is increasing tension between what candidates need to do (or think they need to do) to get nominated and what it takes to get elected.

Vagueness may still have value for candidates, but as Warren’s decision to release a health plan shows, it’s harder and harder for them to pull off.

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