Of all the potential serious candidates for the Republican presidential nomination, only one isn’t playing it coy about their ambition. Senator Rand Paul is bypassing the traditional pretense of indecision prior to announcing and is leaving no doubt that he is planning on running in 2016. The Kentucky senator convened a meeting of advisors to plan the start of his campaign today in Washington but, as the Wall Street Journal reported, there was one important person missing from the conclave: Ron Paul, the former House member and perennial libertarian presidential candidate who also happens to be Rand’s father. But while this absence is in one sense a very good thing for his son’s ambitions, the growing gap between Rand and his father raises the question of whether he can win without his father’s supporters.

Putting some distance between himself and his father has always been a prerequisite for Paul’s presidential hopes. While his father was able to count on a small but active segment of those who voted in Republican presidential primaries, his extreme libertarianism and foreign-policy views that put him to the left of President Obama ensured that Ron Paul never was going to be nominated by the GOP, let alone win the presidency.

Rand had a different plan. Much slicker and more attuned to mainstream opinion than his father, the senator’s goal was to hold on to the libertarian base that he presumed he would inherit from his father and add Tea Party Republicans who admired his principled stands against taxes and spending. Paul won the admiration of a wide range of conservatives last year with his filibuster against President Obama’s drone policies even if many didn’t agree with him on the issue. In an environment in which his neo-isolationist views, carefully parsed to avoid the label of extremism that stuck to his father, had become respectable, Paul was certain to be a first-tier primary candidate. Moreover, in what is expected to be a crowded field in which none of his potential rivals could count on a base as solid as his, there was a clear, if by no means certain, path to the nomination for him.

For those who have followed the senator for the last few years, his attempts to move into the mainstream on foreign-policy issues has been inextricably linked to his presidential ambitions. Though he was an ardent follower of his father when he began his political career, over the course of the last four years in the Senate he has carefully edged his way back into the mainstream. He eschewed his father’s extreme positions on foreign policy and tried to position himself as the avatar of a new generation of foreign-policy “realism.” That put him at odds with neo-conservatives and others in the party’s center on a whole range of issues but was a far cry from his father’s ranting about American imperialism and rationalizations of the behavior of Iran and other Islamist terror sponsors. He tried the same delicate dance on the issue of Israel in which he continued to oppose all foreign aid but also claimed to be a friend of the Jewish state and an opponent of those who would pressure it.

But the senator shocked some of his original libertarian fans recently when he realized that the isolationist moment had ended and endorsed air attacks against ISIS terrorists. In doing so he did what all people who have caught the presidential bug do when they think they have a reasonable chance of winning: abandoning their old positions in the vain support of those who would otherwise not vote for him. That makes Rand Paul a normal politician but it also brands him as a turncoat to his father’s libertarian true believers.

Moreover, in case anyone was in doubt as to what Ron Paul thought about this, they only had to follow him on Twitter where, on election night last week, he had this reaction to a Republican victory that his son was very publicly celebrating:

Republican control of the Senate = expanded neocon wars in Syria and Iraq. Boots on the ground are coming!

This statement changes the dynamic for his son’s presidential campaign. The more Ron Paul denounces the mainstream Republican Party and stays away from his son’s campaign, the easier it will be for his son to ignore those who will say he needs to be held responsible for his father’s extremism. Rather than being Rand’s Jeremiah Wright, Ron may well have no trouble denouncing his son’s apostasy from the libertarian true faith. That will help Rand get more centrist or conservative votes but there’s one element to this equation that doesn’t work in his favor.

It’s one thing for Rand to distance himself from his father’s beliefs but quite another for the Paulbots that energetically campaigned and voted for Ron to abandon him. The plan was, after all, for him to retain his father’s backers while adding mainstream Tea Party or mainstream Republicans who wanted no part of the senior Paul’s extremist views on foreign policy. But if they abandon him altogether, then he will be heading into the primaries without the core constituency that gives him such a strong profile.

The math of the Republican primaries is such that if the Paulbots don’t turn out for Rand it’s hard to see how he wins. Though his father’s following comprised only a minority of GOP voters, they were ardent and well organized, enabling them to win delegates for him in caucus states even though they didn’t represent the views of most Republicans. Added to his new more mainstream fans, they could provide the shock troops of a libertarian push to win the GOP for Rand. But in their absence (and most would stay home or return to their Democratic roots rather than embrace a man whom some would call sellout), Rand will be on an equal footing with other Republican candidates and that spells defeat for him.

This illustrates how difficult it is for an outlier to become a mainstream candidate. Though many libertarians would stick with Paul, if enough don’t, he will wind up falling very short of his goal. Though his father provided the inspiration for his political career, it may be that he will also help end it.