Sen. Rand Paul (R-Ky.), seen by many as the political heir to a libertarian Republican revolution started by his father Ron Paul's 2008 and 2012 presidential runs, has suspended his campaign after just one state voted: an Iowa caucus in which Rand pulled less than half of what Ron did in 2008 in percentage terms, and less than a quarter of what Ron Paul pulled in 2012.

What went wrong, and why? Insiders and outsiders, libertarians and conservatives, journalists and social networking thread commenters, have set theories a-flying. Based on wide reading and talking with people from the Paul world, throughout the campaign and since it collapsed, here are the dominant theories (though many observers think more than one was likely at play).

1) Rand Paul Wasn't Enough Like Ron Paul to Build Off His Father's Success.

Many in the field of libertarian activism just were never satisfied that Rand would stand firm for some of the aspects they most loved about Ron, particularly a firmly no-intervention-unless-attacked foreign policy combined with a surprising empathy toward how our "enemies" might perceive the U.S. as a malign player on the international scene.

Thus, things like Rand's seeming to repeat anti-Iranian talking points or seeming willingness to wage war against ISIS deflated their desire to give money, time, or talk him up everywhere on the Internet as so many did for Ron. This is an idea that you were likely most exposed to not from the mainstream media either print or digital but from following old Ron Paul fans on social networking.

Their disenchantment had a lot to do with, not so much specific words out of Paul's mouth (the Iowa speeches in the last weeks that I saw on YouTube were quite solid in libertarian terms) about his political beliefs or likely actions as president, but with his lack of willingness to be a near-complete Party pariah.

Such concerns began way back in 2012 when Rand, like a good Party man, endorsed Mitt Romney before he was officially the Party's nominee (many Ron faithful believed til the end in some convention floor miracle). Those concerns were compounded by Rand's willingness to stand up for his fellow Kentucky senator Mitch McConnell and other sitting Republicans against possibly more anti-state challengers.

These are the type of fans who might just value pugnaciousness above political effectiveness. (Not that Paul's playing nice with the Party seems to have helped in any obvious way with this presidential run, though it may be vital to his Senate effectiveness moving forward.) But to many Paul fans, and Tea Partyers, a general mistrust of the established Party and its figures was key to their support. Turning around and becoming pals with and respected members of that establishment just made such potential supporters mistrust his and his team's intentions and core spirit.

Even on issues where Ron had or flirted with positions that made some libertarians uncomfortable, such as immigration and abortion, Rand managed to make those positions even less palatable by proposing an essential federal ban on abortion and demanding border walls rather than suggesting they aren't such a great idea because they might someday keep us in, like Ron did in a presidential debate.

Even in areas where he was still a stonger libertarian than any other choice this year, some just had their enthusiasm sapped because you weren't apt to hear a Rand Paul mocking the idea that heroin needed to be illegal to keep everyone from using it, as Ron did in a debate.

The fact that Rand hired pretty much all established political professionals and no diehard Paulian libertarian ideologues for his campaign staff also made some old Ron fans think the campaign was designed to hobble libertarian radicalism from the get-go. Many detected that even when Rand or his people could explain how his particular stances weren't really unlibertarian or that different from Ron Paul's, on things from foreign aid to intervention to abortion to drugs to military budgets, the very complications or equivocations that led to such explanations even being necessary ruined the ideological and moral clarity that helped Ron win so many fans.

Drew Ivers, a higher-up in both of Ron's Iowa runs, declined from the beginning to get involved in working for Rand, though he voted for him and still has political fealty to the Paul family. He saw, Ivers says, a strategy he was sure would fail exactly as it did: "Rand comes from the liberty, right-wing, the small government wing of the party and [trying to pull from or appeal to other sides] just muddled the message."

Rand Paul himself has, since the campaign suspension, noted the annoying, to him, irony of being accused of losing steam for being insufficiently purist libertarian, and also accused of having lost potential scorched-earth anti-establishment constituents to Donald Trump.

2) Rand Paul Didn't Get to Campaign in the Political Environment He Wanted and Expected

Both the actual GOP field, and the world around him, didn't deliver the environment that Paul and his team expected or needed to thrive. Certainly the perceived rise of ISIS and the possibility of domestic terror threat made many voters eager for a more bellicose foreign policy voice than Rand delivers.

Daniel McCarthy (a veteran of Ron Paul's 2008 campaign) explains in American Conservative that the Paul team expected Marco Rubio and Jeb Bush to be the major opponents, and Paul could never be as much of an evangelical-free-market cross-appeal player as Ted Cruz has so far seemed to be. Running a purely insurgent anti-establishment campaign like Paul did will never be enough, especially in an environment with a more colorful nearly anti-libertarian anti-establishment insurgent like Donald Trump.

At Rare, Paul's former assistant and co-author Jack Hunter lays the blame pretty solidly on the presence of Trump. Hunter raises the question (that has also been haunting me as author of Ron Paul's Revolution, a history of Paul's political career and presidential campaigns) of whether the Ron Paul movement might have been less about libertarian ideas, and more about scorched-earth anti-establishment outsiderism, than we'd thought or hoped. Hunter also, on the optimistic tip, points out that at least stated opposition to the Iraq war and later interventions such as Libya has switched from a Paul family monopoly to a belief of both current GOP frontrunners.

David Boaz of the Cato Institute, writing in USA Today, rightly laments all the fresh ideas on criminal justice and specific constitutional liberties that Paul uniquely brought to the GOP table, and notes the (undoubtedly unexpected by Paul's campaign in the beginning) failure to attract any seven figure SuperPAC support from the very wealthy. For whatever reason 2016 was not the fundraising environment Paul hoped or expected.

Ivers of Iowa thought from the start that 2020, or even further down the road, might be Rand's real chance, giving him the opportunity to build a reputation as a national liberty leader in the Senate unsullied by any compromising needs perceived for a presidential run, especially given how impeccable he finds Rand's Senate voting record. Ivers would make ophthalmologist jokes with Rand, he says, about: "How's your 2020 vision?" While Ivers says he does not know for sure, he thinks it likely that Rand might have had his fill of running for president after this experience.

3) Rand Paul Was Trying to Do Something Impossible, So No Wonder He Failed.

Maybe, maybe a candidate as libertarian as Rand Paul is just absolutely not what Americans really want right now, no matter who your staff is, how you sell yourself, who your opponents are, or how much money you raise.

It could be that conservatives are so metaphysically opposed to the conception of rights that generally undergirds libertarianism than any attempt to meld the two within the two party system is going to collapse from the weakness of its own philosophical foundation, as was roughly argued by Tom Mullen at Huffington Post, so that ultimately "Paul's attempt to fit the libertarian message into a conservative framework killed his chances" by making him unpalatable to both sides of that divide.

Gary Johnson, 2012's Libertarian Party presidential candidate and seeking the same honor in 2016, agrees that the GOP is no place for liberty: "Rand Paul is the latest to find that there is no room for the Liberty Movement in today's Republican nominating process. I've been there. With his departure from the presidential race, there is no voice remaining to challenge failed military interventions, mass surveillance of Americans by their government, or real cuts in the size and cost of government."

Molly Ball at The Atlantic reported from her own experience seeing Paul try to sell things to select groups of influential Republicans in Iowa and New Hampshire in the early days of the campaign. When Paul pushed an attitude toward immigration involving finding places to work here for people who wanted to work, or a punctilious respect for civil right and constitutional procedures even against terror suspects, she saw that the GOP base clearly wanted nothing to do with such heresies.

At Pajamas Media, Walter Hudson also believes that it is a overwhelmingly a simple matter of the American people, whether in or out of the GOP, in 2016 having no demonstrated interest in what Paul is selling, that:

Right now, people don't want liberty. They may want a sense of freedom for themselves, but aren't willing to endure their neighbor's freedom. Modern Americans will sacrifice their own rights to wield control over others. If you doubt that, attend your town's next planning commission meeting. For freedom to reign, the culture must change, and a political campaign is not going to do that.

Hudson further laments conspiratorial and personality-centered thinking among libertarians that refuse to recognize that the above is the real problem.

Some insiders had more nuanced takes, including some different elements. Matt Kibbe, formerly of the Tea Party-ish grassroots group FreedomWorks and this cycle working with the Paul-supporting SuperPAC Concerned American Voters, saw some self-sabotaging irony: He saw post-Ron Paul figures who he thinks his revolutionary energy helped bring to prominence, such as Cruz and Rubio, sucking up some votes that might have been Paul's.

A similar irony: Kibbe knows some students whose presence the campaign specifically roused to caucus ended up hypnotized by Bernie Sanders as the anti-crony capitalism figurehead and caucused for him instead.

How to deal with youngsters who get energized by an anti-establishment figurehead, whether a Bernie or Trump, but don't seem to get the libertarian version of the anti-establishment message? One thing Kibbe thinks may work better is shifting libertarian persuasion emphasis from big ideas in and of themselves to specific stories of government failure and unintended consequences of its seeming good intentions.

Rand Paul perhaps summed up what we actually know versus what we might surmise himself in a statement to Associated Press reported by Concord Monitor. "I don't really have an absolute answer for what went on with the election and why people make their choices…But I do think our voice was an important one and I think as people look backwards they are going to say they were happy to have my voice in the debate."