How Voters Actually Decide: What Field Experiments Reveal About Persuasion
The gap between how campaigns think voters behave and how voters actually behave is enormous. Political science has spent decades studying this gap, and the findings are surprisingly consistent. The most useful way to understand it is to look at what field experiments—real-world tests with control groups—have found about the persuasive effect of campaign contact. The short answer is that direct persuasion barely moves anyone, yet the entire campaign industry is built around trying to do exactly that.
The core problem is what G. Elliott Morris named the Strategist's Fallacy in October 2025: the belief that voters hold positions and match them to candidates like an entree off a menu. Under this view, a campaign’s job is to present a better menu and convince voters to switch their order. But decades of survey research show this is wrong. Voters do not think in left and right. Most people do not carry a coherent ideological framework at all. Political scientists have known this for a long time. Back in the mid-twentieth century, Converse found about one voter in nine reasons ideologically. More recent work by Kinder and Kalmoe found that share has barely moved. Morris puts it at 10 to 15 percent. That means roughly 85 to 90 percent of voters are not matching candidates to a pre-existing set of policy positions.
So if voters are not ideologues, what drives their choice? The strongest answer is party loyalty. Most voters decide based on partisan identity long before any campaign ad airs. They are not weighing issues so much as they are affirming who they are. This is why the concept of persuadable voters is so narrow. True swing voters—people who could genuinely go either way—are a small slice of the electorate. And even among that slice, the evidence suggests they are not persuadable in the way campaigns hope.
The most rigorous evidence on this comes from a major review of field experiments. Across 49 field experiments, Kalla and Broockman’s best estimate of campaign persuasion in a general election is zero. Not small. Zero. That means door-knocking, phone banking, mailers, and digital ads do not, on average, change a single vote in a general election. What campaigns actually do is not persuasion but mobilization—getting people who already support you to show up. That is a fundamentally different task, and it is one the industry has largely confused with the other.
This is not to say that voters never change their minds. They do, but the change usually comes from big, slow-moving forces, not from a clever ad. The clearest example is the fundamentals model Morris built for the 2024 election. His two-input model, based on economic conditions and approval ratings, forecast Harris at about 48 percent of the two-party vote. She got 49.3 percent. That is a miss of just over one point. On conditions alone, Trump wins about nine times in ten. The three decisive states turned on 229,766 votes. That is a razor-thin margin, but it was almost entirely predictable from structural factors, not from persuasion. The campaign that spent hundreds of millions on persuasion did not move the needle; the economy and incumbency did.
This leads to the moderation debate that plagues both parties. If persuasion does not work, then why do candidates fight over the center? The answer is that they are fighting over a myth. Broockman and Skovron found that legislators in both parties overestimate how conservative their constituents are. They think voters are more right-wing than they actually are. That misperception drives a lot of moderate positioning. But if voters do not think in left and right, then moving to the center is not a rational strategy for winning over persuadable voters; it is just a way to avoid losing your own base.
The real debate among strategists is about what this all means for the future. Some argue that since persuasion is dead, the only path is to turn out your existing coalition. Others, including the WelcomePAC report Deciding to Win, recommend a 2028 Democratic nominee willing to break with progressive advocacy groups. That recommendation assumes that breaking with the left will win over moderates. But the field experiment evidence suggests that assumption is shaky. Moderates versus progressives is a real tension inside a party, but it is not the same as a strategy for winning general elections. If persuasion does not work, then the fight over ideological positioning is largely about internal party identity, not about changing voters’ minds.
None of this means campaigns are useless. They are essential for mobilization, for fundraising, and for defining the narrative in the few weeks before an election. But the honest conclusion from Daily Political Press science is this: voters decide based on who they are, not on what you say. The sooner campaigns accept that, the less money they will waste trying to convince people who were never listening.
