Stop me if you’ve heard this one before: Independent voters will decide the election. Or better yet: Moderate voters will decide the election. Or, wait for it … If Democrats can move to the middle, they will win in 2020.

These tropes conjure up a particular image: a pivotal bloc of reasonable “independent” voters sick of the two major parties, just waiting for a centrist candidate to embrace a “moderate” policy vision. And there’s a reason this perception exits: You see just that if you look only at topline polling numbers, which show 40-plus percent of voters refusing to identify with a party, or close to 40 percent of voters calling themselves moderates. But topline polling numbers mask an underlying diversity of political thought that is far more complicated.

Moderate, independent and undecided voters are not the same, and none of these groups are reliably centrist. They are ideologically diverse, so there is no simple policy solution that will appeal to all of them.

To better understand the unbearable incoherence of moderates, independents and undecideds, let’s start by visualizing them. Drawing on data from the Democracy Fund Voter Study Group, a research consortium that works with YouGov to conduct large-scale surveys, I pulled voters who …

Identified as “moderate” Identified as “independent,” even when pressed to pick a party Said they were undecided on how they would vote in a 2020 match-up between President Trump and a generic Democrat.

Here’s how big each group is in the electorate overall, and how much they overlap:

Despite some overlap among independents, moderates and undecided voters, each group is relatively distinct. However, this doesn’t necessarily mean there are cohesive ideological beliefs within each group.

To test this, I used policy questions from the same Voter Study Group survey to make two indexes measuring attitudes on economic policy and immigration. I chose these two issues because they are perhaps the two most central in national politics, and they represent competing dimensions of political conflict — few voters hold consistently middle-of-the-road opinions on both issues. The indexes range from -1 (far left) to +1 (far right).

Overall, the electorate ranges widely along both dimensions. But broadly, there are two major clusters: Democratic voters populate the lower-left part of the distribution (liberal on both economics and immigration), and Republicans populate the upper-right part of the distribution (conservative on both issues).

Independent voters, however, come from all over the ideological map:

Some independents are market-oriented and anti-immigration. More are the opposite. Many are consistent liberals on economic and immigration policy questions. Some are consistent conservatives. Some are somewhere in the middle. So, next time anybody says that some policy position will win over genuine independent voters, they aren’t addressing an obvious question: Which independent voters?

Are independents also “moderates?” It depends how you define “moderate.” If you define moderates based on self-identification, then the answer is: sort of. More than half — 58 percent — of self-identified independents in the Voter Study Group data also identify as moderate, compared to 27 percent who identify as conservative and just 15 percent who identify as liberal.

But many people who call themselves “moderate” do not rate as moderate on policy issues. Just like self-identified independents, moderates come from all over the ideological space, including moderates who also identify as independent.

But unlike independents, moderates are more likely to be Democrats. The average moderate in the Voter Study Group data is solidly center-left on both economic and immigration issues. This, I think, has mostly to do with linguistic history: Republicans have long embraced the “conservative” label, but for decades Democrats ran away from the “liberal” label, leaving “moderate” as the only self-identification refuge for many Democrats. (Only recently has “liberal” again become a fashionable identification for the left.)

Consider the typical ideology survey question, which gives respondents three options: liberal, moderate or conservative. A voter who identifies as neither liberal nor conservative has only one other option: moderate. And moderate sounds like a good thing. Isn’t moderation a virtue?

As the political scientists Donald Kinder and Nathan Kalmoe put it, after looking at five decades of public opinion research, “the moderate category seems less an ideological destination than a refuge for the innocent and the confused.” Similarly, political scientist David Broockman has also written about the meaninglessness of the “moderate” label, particularly as a predictor of centrism.

The takeaway is simple: As they must with independents, any pundit who talks about “moderates” as a key voting bloc begs that second follow-up question: Which moderates?

Finally, let’s turn to those mythic undecided voters who are supposed to determine the future of the nation. What about the 11 percent of respondents who said in the Nov. 2018-Jan. 2019 Voter Study Group survey that they weren’t sure yet how they would vote in 2020?

Like independents and moderates, undecided voters also defy simple categorization. They also come from all over the ideological map. While pundits love to speculate and generalize about undecided voters, undecided voters themselves eschew easy summary judgments.

The upshot of all this is that if you’re a campaign trying to appeal to independents, moderates or undecided voters — or a concerned citizen trying to make sense of these groups in the context of an election — policy and ideology aren’t good frames of reference. There just isn’t much in terms of policy or ideology that unites these groups.

Anybody who claims to have the winning formula for winning moderate, independent or undecided voters is making things up. Perhaps more centrist policies will appeal to some voters in each of these categories — but so will more extreme policies.

And come election day, these potential swing voters may not ultimately care all that much about policy. They don’t tend to identify themselves based on ideology, and they don’t follow politics all that closely. They’re more likely to decide based on whatever random events happen at the last minute (like, say, a letter from the FBI director). These are even harder to measure and generalize about. (The good news for pundits and campaigns is that they leave even more room for open speculation and political fortune-telling.)

But OK, one final point needs clarification here — maybe we’re being too literal: Maybe what pundits are really getting at when they talk about appealing to “moderates,” “independents” or undecided voters is the “middle-est” middle of the electorate — in terms of vote choice, partisanship and ideology. Maybe they’re talking about people who identify as moderate, independent and are still undecided on 2020 — the part of the Venn diagram above where all three circles overlap.

First, this is a really small group — only 2.4 percent of the electorate falls in all three buckets. And even this super small middle of the middle is … you guessed it … all over the ideological map. Rare as these voters are, anybody who talks about winning over undecided, independent, moderate voters should first address the question: which undecided, independent, moderate voters?