On Tuesday in Louisville, Kentucky, Senator Rand Paul will officially kick off his campaign for president. As the New York Times reported Monday, his father, former Congressman Ron Paul, will be right by his son’s side for the campaign announcement. But don’t expect to see much of the elder Paul throughout the campaign—or hear much from him. While Rand and Ron both consider themselves libertarians, their positions on multiple issues have diverged in recent months as Rand has attempted to make himself a legitimate contender for the Republican nomination. In the process, that has alienated many libertarian supporters of Ron.

While Ron Paul was always an outsider candidate with no real shot of becoming president, Rand has much larger national ambitions. That has required him to make compromises on some of his positions, compromises that many libertarians find unacceptable. Retaining their support will almost certainly be a necessity for Rand to win the GOP nomination. But will they look past his heresies?

Rand Paul has been a savvy political operator during his time in the Senate and has always sought to leverage his libertarian support on issues that had broad acceptance within the GOP. For instance, Paul expertly seized on the issues of criminal justice reform and the overreach of the National Security Agency (NSA). These were long-held libertarian positions that, partially thanks to Paul's advocacy, suddenly found renewed interest among mainstream Republicans. The issues garnered support among conservatives because they would shrink the size of government. They were the perfect issues for him to retain his libertarian credibility while earning greater support among traditional Republican voters.

But recent issues have demonstrated where traditional Republicans differ from libertarians, and that has put Paul in an uncomfortable position. Libertarians like Ron Paul set a very high bar for military conflict. Often, they are called isolationists, a term that has sometimes been used to describe the younger Paul, much to his chagrin. In the early parts of his time in the Senate, Paul displayed many of those leanings. In 2011, for instance, he called for ending all military aid to Israel. As late as June 2014, Paul wrote an op-ed for the Wall Street Journal about the emergence of the Islamic State in Iraq. “Why should we choose a side, and if we do, who are we really helping?” he asked in the piece. Just a few months later, after the Islamic State murdered two American journalists, Paul condemned President Barack Obama for not doing more to stop the terrorist group.

Over the following nine months, Paul’s remarks about the military and his policy positions have seemed to become more and more hawkish. Last October, he gave a speech on military intervention that you could never imagine his dad giving. “The war on terror is not over, and America cannot disengage from the world,” he said. “To defend our country we must understand that a hatred of our values exists, and acknowledge that interventions in foreign countries may well exacerbate this hatred, but that ultimately, we must be willing and able to defend our country and our interests.” It was quite a rhetorical change from a man who just 20 months earlier performed a 13-hour talking filibuster over U.S. drone use.

In January, Paul made news at a forum hosted by the Koch Brothers when he challenged the traditional Republican line on military action. “Are you ready to send ground troops into Iran? Are you ready to bomb them? Are you ready to send in 100,000 troops?” he asked senators Marco Rubio and Ted Cruz, who had criticized the Iran negotiations. “I’m a big fan of trying to exert and trying the diplomatic option as long as we can. If it fails, I will vote to resume sanctions and I would vote to have new sanctions. But if you do it in the middle of negotiations, you’re ruining it.” That was music to the ears of libertarians everywhere. Maybe, they thought, Paul would actually stick to his libertarian roots on foreign policy.

Nope. In early March, Paul signed on to Senator Tom Cotton’s letters to the leaders of Iran, explaining why the American political system effectively prohibited Obama from making any lasting commitments in the negotiations. The letter received widespread condemnation, including from many within the Republican Party. But in libertarian circles, Paul’s signature was treated as almost an act of treason. At the Daily Beast, Olivia Nuzzi reported on a number of libertarian leaders who declared Paul’s signature the final straw; they would no longer support him for president.

At the end of March, Paul proposed a massive increase in defense spending, raising it more than $190 billion over the next two years and offsetting those increases with cuts elsewhere. As Bloomberg’s Dave Weigel reported at the time, this doesn’t quite represent a flip-flop. But it’s still quite a change from Paul’s 2011 budget which would have reduced defense spending to $542 billion in 2016, including additional war funding. Under his new plan, defense spending would be nearly $700 billion in 2016.

As his 2016 officially kicks off, Paul will have to strike a balance between appeasing the defense hawks and libertarians within the Republican Party, both of whom view him suspiciously. To some extent, his movement back and forth between the factions has made it unclear what his foreign policy views actually are. Last week, for instance, as Republican candidates criticized the president’s deal with Iran, Paul stayed noticeably quiet. When his staff finally responded to questions to Bloomberg on Monday, they offered little insight into Rand’s actual position on the deal. That tactic—sidestepping the question—will work for now. But eventually it’s going to fail as Republican voters and donors will demand his position on different foreign policy issues.

The good news for Paul is that his positions on the NSA and criminal justice reform, among other issues, still play well within the party. More than any other candidate, he has made a concerted effort to reach African Americans. These are all libertarian positions that will play well for him during the primary. But it will still be hard for many Ron Paul followers to overlook—or brush off—Rand’s turn to hawkishness on foreign policy, assuming he goes in that direction. For instance, Nick Gillepsie, the editor in chief of the libertarian magazine Reason, calls Paul “libertarian-ish,” not a libertarian.

Do Republican primary voters want a “liberatarian-ish” candidate? We’ll find out soon enough.

Correction: A previous version of this article referred to the National Security Agency as the National Security Administration.