The political independent is a curious thing. This human is neither affiliated with nor loyal to any political party. In many ways, this is the fashionable place to be. The independent has long been defined as a discerning voter, one who can go in any direction, and deliberates thoroughly before choosing the best candidate, often breaking en mass one way or the other only days before the voting begins. Being independent rises above the pettiness of partisan games. They are the wise. This is what helps ensure its status as a fashionable (non) affiliation.
It is more than no party
the true independent is rare, like finding an albino in the wild
An independent implies no loyalty to any party. The ballot of an independent is one that is all over the partisan map, and it remains random from one election to the next. We can count on a partisan to vote for their party in each election. An independent is voting for any, filling their ballot with votes for those of various parties along with other independent candidates. One year, they vote Republican. The next, they vote Communist. Then it is a Libertarian, followed by a Democrat. In short, the independent is mad. Moreover, this is why the true independent is rare, like finding an albino in the wild.
Two kinds of independents
There are a few different kinds of independents, but there two most common are 1] low-information (passive) voters and 2] partisan voters who are "independent" only in a technical sense. The first group are more likely to resemble to mad independent described above. They rarely vote, and when they do, they vote for who their partner or passionate friend strongly suggests, and thus have a random voting history, only casting ballots when galvanised, possibly determined more by dating patterns than partisan or ideological ones. The other group are those who are just as partisan, and some studies suggest are more so, than any other partisan is. They simply choose not to formally affiliate. This could stem from residing in a state that does not register voters by party affiliation, or because they like the unearned credibility media gives them when describing themselves as independent (objective, studious, discerning, et cetera). Perhaps it stems from simple disgust at what many of their party has done once in office, choosing instead not to publicly wear the tainted badge of their team - a sort of "Not Me" when, yeah, it is totally you.
Those are the two Big Ones. Media needs to get hip to this reality and cease presenting independents as being a collection of oracles and sages. The majority of independents are, in many ways, political simpletons.
Such magnanimous acts of non-partisanship does not make an independent
Some pride their status, and as proof, they will cite how they "voted Republican" in the last election, but leave out all the details, such as how they always vote for Democrats for all major offices, yet like to throw in a vote for a Republican for some local county seat from time to time. Another may always vote for Republicans, except that one time ten years ago. Still others may engage in long-term ballot splitting, such as always voting for Democratic statewide officials, while voting Republican for federal offices. Such magnanimous acts of non-partisanship does not make an independent - neither the mad nor the discerning.
The Party is the Church
Everyone knows none are indoctrinated into a religion. Humans are freely inspired and follow a faith of their earnest choosing. This is why virtually everyone born and raised in Mexico are Catholics, in Saudi Arabia they are Sunni Muslims, in Sweden they are Protestant, in Iran they are Shia Muslims, in India they are Hindu, in Russia they are Orthodox, and so on. It is entirely random.
We find this randomness in party affiliation. If a human is born and raised in a Democratic home, they are very likely to be Democrats in adulthood. In fact, we may take this religion example a bit further. If one is born and raised in a Catholic home, they very likely will be a Catholic adult. However, some may leave the church but are very likely to remain Christians. Less common it they becoming atheists. Even less common than that is converting to Islam. A liberal Democratic household is likely to produce a liberal Democrat, but if they leave the party, they very likely will remain liberal voters. Less common is permanently choosing to abstain from voting. Even less common than that is becoming a conservative and registering with the Republican Party.
Certainly, other environmental factors may influence things, as with religion. To begin, religion tends to influence a great deal - humans attend services and find themselves surrounded with friends of the same faith. If a Christian household, but in Iran, it is possible the developing youth will take on more influence from their surroundings outside the home than within it. Regardless, politics does not lend itself to weekly services reinforcing doctrine. Therefore a liberal Democratic household, though likely to produce a liberal Democrat, can find themselves with a conservative Republican child because that child, while coming of age, was surrounded by conservative Republicans everywhere outside their household and lacked a comparative weekly indoctrination service. This is to say, then, that the same two factors that determine religion (location and household) also influence partisan voting (location and household).
The South has always been conservative
One way to consider this point is to look at the Southern United States. During their Revolution, the greatest concentration of Loyalists (as opposed to Patriots) was in the South. Being conservative, this made sense. Maintaining the status quo, sticking with traditional values, opposing radical change, et al. The large concentration of Loyalists had everything to do with the British Southern Strategy. Later, the South, remaining conservative, kicked off a great Civil War trying to preserve the antebellum South (AKA traditional values, states' rights, resisting progressive change, et al). Southern political leaders brought about Jim Crow laws to return black Americans to a state of second-class citizenship - a traditional value of the time. These political leaders sought to defeat efforts of progressive change, often arguing state's rights and traditional values ever since. It is and has always been a conservative bastion.
What has changed over all of that time is the political parties dominating the South. For the first 150+ years of its history, Democrats held sway over the conservative South. They were the conservative party for generations. The Radical (left-leaning) Republicans came along and were the progressive party for a number of generations. There followed a period where both parties had liberal and conservative blocs, but since the nineteen-fifties, the conservative Southern Democratic bloc started to break away from their liberalising national party, first by creating "Dixiecrats" and, eventually, flipping to the Republicans as they became the conservative party. The political philosophy of the South has, for the most part, remained fairly static (e.g. conservative), while the principal political philosophies of the parties have flipped their ideological mooring.
Therefore, a human born and raised in the South, within a conservative household retaining its traditional Democratic affiliation, is likely to mature into a conservative Republican voter. This flip, however, is less dramatic than the liberal Democrat flipping to a conservative Republican. This creates an impression of political independence, but it is not true independence. Perhaps, if using the religion analogy again, this conservative Democrat flipping to a conservative Republican, within a sea of other conservative Republicans, is akin to a Southern Baptist flipping to a Southern Methodist. It is a mild change, as they are still Protestant Christians.
Independents Decide Elections
The media loves to say that independents broke for one party, and that is how they won. The candidate who wins the independent vote is seen as the one selected by the discerning voter, and is given some amount of extra gravitas for winning that coveted voting bloc. The data will show this claim to be true. If the electorate was 30% independents, and 60% of them voted for the Republican, than it is technically true the Republican won the independent vote. The problem, however, is voter turnout. What this scenario is actually saying is that "independents" who always vote for Republicans showed up on Election Day in greater numbers than did "independents" who always vote for Democrats.
I am happy to date and be friends with benefits, but I will never call you my girlfriend!
The passive, low-information independent will always be around. It is the nature of being passive and generally uninterested in politics. However, the majority of independents need to own their shit. These humans are not independents, and they know it. They can prove it: which political party won their vote for the major offices in the past, say, four elections? Twenty Republicans, two independents, one Libertarian, and one Democrat? This is not independent voting. This is, in fact, a voter who can reasonably be relied on to vote for Republicans, if and when they show up to vote, and should just own their bullshit rather than lying to everyone. Though true, there is the mad independent, and those passive voters, but if a politically engaged human ever tells you they are an independent voter, it is a safe bet to read that pronouncement as "I am a liar!" or "I am happy to date and be friends with benefits, but I will never call you my girlfriend!"