A year ago, if you had asked me whether Chris Christie, Scott Walker, or Rand Paul would be the last man standing of those three, I would have told you Rand. Christie would surely drop out early, done in by Bridgegate and his sheer RINO-ness. Walker was a serious threat to win, but there was a real chance that his voters would be gobbled up by more talented center-right and conservative retail politicians like Marco Rubio and Ted Cruz. Paul, however, had his own niche. Libertarians are a smallish minority of the GOP but even a smallish minority can be a force in the early states when the field’s divided among many candidates, as Rand’s dad could tell you. There was reason to think he would inherit the lion’s share of Ron’s support in Iowa and New Hampshire while adding some “conservatarian” votes from mainstream Republicans who want something different in the next nominee. It wasn’t hard to imagine him winning 20-25 percent in both states.

He’s at 2.4 percent in RCP’s average of national polling and may well be the next domino to fall, especially with Republicans pressuring him to help them hold onto the Senate by dropping out soon and defending his seat. What happened?

One unnamed New Hampshire Republican told the Beltway publication that Paul’s “campaign (reeks) of the same stench of death that surrounded the Perry and Walker efforts before their demise.”…

It has been death by a thousand cuts for Paul’s campaign: reports of staff infighting, the federal indictments of two longtime aides, lackluster fundraising, the improbable and unpredictable rise of Donald Trump, and a Republican Party that appears to be returning to its roots on foreign policy…

The third-quarter fundraising period ends Wednesday, and one of the biggest questions will be whether Paul has raised enough money to continue his quest.

Paul’s campaign has spent the last few days feverishly sending fundraising emails, begging for contributions to keep Paul’s leaky ship afloat.

I can buy that the GOP is more interventionist today than it was in 2012, when Ron Paul nearly won Iowa and finished second to Mitt Romney in New Hampshire with nearly 23 percent of the vote. I can’t buy that it’s so much more interventionist, the rise of ISIS notwithstanding, that it would drop Rand Paul from Ron’s numbers to low single digits in the polls. I think that decline is a function of my initial impression about Rand being wrong: It turns out he doesn’t really have “his own niche” in the race. Paul, as I said, was trying to build a coalition of libertarians, “conservatarians,” and more generally anti-establishment Republicans and independents who are tired of politics as usual. Ted Cruz ate up most of the “conservatarian” vote, I think, by giving mainstream righties who like Rand a small-government alternative minus the kookiness and isolationist pedigree that conservatives never liked about Ron Paul. Rand, meanwhile, forfeited some of his father’s libertarian base by simply being too mainstream on certain issues, particularly issues related to foreign policy. One obvious flashpoint was the Iran deal. Ron supported that, as you’d expect him to; any diplomacy that averts war, if only in the short- to medium-term, is apt to be cheered as a victory by isolationists. Rand opposed the deal, however, because it didn’t demand proof of denuclearization before granting sanctions relief. Rand also signed Tom Cotton’s open letter to Iran warning them that any deal with the U.S. would cease to be binding until it had been approved by Congress — a letter denounced by Ron Paul as designed to “stop peace.” I think a lot of libertarian Ron Paul fans looked at that, along with Rand’s slipperiness on various other foreign policy questions, and decided that he couldn’t be trusted as president to resist interventionists.

Ultimately, though, it may have been Trump who did Paul the most damage by siphoning off all the Republican and indies who were looking for an outsider to “shake up the system” as president. Go look at the polls in New Hampshire for Rand before and after Trump got into the race. Throughout April, May, and June, he was consistently in double digits there; the growing field knocked him down to nine points or so by mid-June, but that’s still a respectable early figure. Six weeks later, though, as Trumpmania took off and Trump soared in the polls, he was in the low single digits and has never recovered, landing at just three percent in the latest poll taken there. The debates haven’t been good for him either, as you can see here in HuffPo’s tracker of his favorable rating:

He was already 10 points underwater on average by the time of the first debate on August 6th. Since then he’s slipped another three points, likely due to a combo of him going after the newly popular Trump and getting into a high-profile fight with Christie over the NSA. My sense of the GOPers and indies who like Trump is that they’re emphatically not isolationists; Trump likes to describe himself as “militaristic” and boasts, as part of his “Make America Great Again” message, that he’ll make the military bigger and better than ever as president. The implication from his comments about going into Iraq and Syria and taking the oil controlled by ISIS is that the U.S. will start showing people who’s boss again once President Trump is in command. That’s the opposite of the Paul approach to foreign policy, something the debates have highlighted. Between Cruz, Trump, and disaffection on both sides — libertarians and Make-America-Great-Again-ers — Paul’s left with basically no voters. How much longer can he go on?