The New Republic is watching U.S. Sen. Rand Paul (R–Kentucky), and it’s worried:

It was the first time in recent memory that the Iowa GOP Lincoln Day Dinner sold out nearly two weeks in advance, and it was on the strength of its headliner, Kentucky Senator Rand Paul, who, in turn, was invited on the strength of his 13-hour filibuster against the Obama administration’s use of drones. …

In fact, in the months since Rand Paul’s blockbuster filibuster, the news cycle has handed him gift after gift after gift. Not long after the IRS revelations came the Department of Justice’s aggressive pursuit of national security leaks to the Associated Press. Then news broke that the National Security Agency was dredging up massive amounts of telephone data from millions of Americans on a daily basis. Paul quickly threatened to bring a class action lawsuit against the agency. This is a moment tailored for Rand Paul, more than for Marco Rubio or Chris Christie, or anyone else in the potential Republican 2016 lineup.

And yet, in Iowa, Paul wasn’t completely content with easy applause. He didn’t even mention the IRS. What he really wanted to talk about, he told the crowd, “is immigration.” Earlier, King and Grassley had sounded defiant, nativist tones, condemning the moderate legislation suggested by the Senate’s Gang of Eight. Paul, however, voiced his disagreement and laid out his own proposals to reform work visas, secure the border, and legalize the migrants that are already here. The room grew noticeably quieter. “I also think that, as a party, we need to grow bigger,” he said to an audience that was entirely white, save for a lone Sudanese immigrant. “We’re an increasingly diverse nation, and I think we do need to reach out to other people that don’t look like us, don’t wear the same clothes, that aren’t exactly who we are.” The GOP, he said, needed to be more respectful. By this point, the crowd was silent.

Later, Paul told me that it was a good silence, the silence of people listening. “The Democrats have done a better job of being a party of people from all walks of life, and we need to do that,” he said. “We need to have working-class folks, we need to have people with earrings, nose rings, tattoos, ties, without ties, ponytails, no ponytails. One of the things where my dad was successful, was when you went to his rallies, you saw people from all walks of life.” And by the time Paul was done speaking that night in Cedar Rapids, by the time he showed that appealing to minorities was, also, a matter of utility, a strategy to once again become “the dominant national party,” the crowd was again up on its feet, hooting and applauding.

When Paul launched his political career three years ago, he was viewed in much the same way as his father, or, as Senator John McCain once called him, a “wacko bird.” He was identified with the same marginal issues (drug legalization, neo-isolationism) and the same marginal constituencies (anarchists, goldbugs). But this year, Paul has emerged as a serious candidate. He has started actively campaigning for the nomination earlier than any of the other Republicans mulling a run. Already, he has racked up multiple meet-and-greets, dinners, and coffee gatherings in Iowa, New Hampshire, and South Carolina. While his father may have been an also-ran, national polls show Rand Paul as one of the top contenders for the GOP nomination. In private, Paul has been meeting with key GOP power brokers, including the Koch brothers, and he has courted techies at Silicon Valley companies like Google, Facebook, and eBay. “We’re doing something that Ron never did; we’re reaching out to major donors,” says a Paul adviser. “Not everyone is giving us money, but there’s definitely some flirtation going on.” According to this adviser, in the last six months, RAND PAC, Paul’s national political operation, has raised more than a million dollars. “He’s very politically talented,” says a former senior official at the Republican National Committee. “He is absolutely a contender.”

In his efforts to court new audiences, or to bring what he calls “tough love” to friendly ones, Rand Paul is aiming for a bigger, broader base than Ron Paul—or, for that matter, Mitt Romney—ever captured. But though he has staked out more moderate or traditionally Republican positions than his father, at his core, Rand retains the same pre–New Deal vision of hyper-minimalist government and isolationist foreign policy. In other words, Paul has managed to take the essence of his father’s radical ideology—more radical than that of any modern presidential candidate—and turn it into a plausible campaign for the Republican nomination.