Thom Tillis wasn’t Rand Paul’s first choice to take on North Carolina Democratic Sen. Kay Hagan. The senator from Kentucky had endorsed Tea Party candidate Greg Brannon in the Republican primary, stumping for him even when he looked like a long shot.

Yet there was Paul in Raleigh last week campaigning for Tillis, speaker of the state house of representatives. The race is competitive, but Tillis—a quintessential Republican establishment candidate—has trailed consistently and could use the help. A Libertarian Party nominee is siphoning up to 7 percent of the vote, a group Paul is particularly well positioned to try to swing.

According to BuzzFeed, Paul’s campaign appearance on behalf of Tillis moved one of his father’s supporters to tears. In this case it was tears of joy, as the woman was happy merely to meet Rand. Some libertarians feel anything but joy, however, when Ron Paul’s son is seen as a Republican team player.

The father and son share similar philosophical principles but have very different approaches to politics. Whether running for president or actually serving in the House, Ron tended to use the platform to educate people about ideas: Austrian economics, non-interventionism in foreign policy, his critique of the Federal Reserve.

The elder Paul is a lifelong Republican, but over time his party affiliation seemed to owe more to the impracticality of working outside the two-party system than to a belief that the GOP shared his small-government convictions. He briefly left the party to serve as the 1988 presidential nominee for the Libertarian Party, in which he retains a lifetime membership.

Ron spoke at the U.S. Taxpayers’ Party national convention in 1992. He first encouraged his supporters to consider voting for a trio of third-party presidential candidates in the 2008 general election, then specifically if belatedly endorsed Chuck Baldwin, nominee of the Constitution Party, as the U.S. Taxpayers’ Party is now known.

Rand uses politics in the more conventional sense. He seeks to win votes and converts, to forge alliances and build coalitions, to put forth legislation and prevail in elections. He is more comfortable in the Republican Party and committed to working within it.

Consequently, the younger Paul endorsed Mitt Romney for president in 2012. This November he is backing moderate Maine Republican Sen. Susan Collins over a Democrat running on civil-libertarian themes. He supported Senate Minority Leader Mitch McConnell over a conservative primary challenger earlier this year and is traveling the country to help make McConnell majority leader.

Ron Paul’s attacks on U.S. foreign policy were jarring to the average Republican ear, with his passionate denunciation of American empire. Rand Paul tries to reach Republicans where they are and gently nudge them in a less interventionist direction by emphasizing areas of possible agreement between the GOP mainstream and libertarianism, such as defending Congress’s power to declare war and denying a Democratic president’s power to conduct extrajudicial killings of Americans.

When Ron Paul originally sought the Republican nomination, many around him considered it a success if he got to speak out against the Iraq War during candidate debates and publicize his audit the Fed bill. Many around Rand Paul will only consider his likely 2016 candidacy a success if he ends up in the White House.

The differences can be overstated, of course. There is a substantial liberty movement-building component to Rand Paul’s political activities. For all the libertarian grumbling about Rand’s alleged impurities, he stands up well compared to his peers: Sen. Ted Cruz has amply demonstrated the political potential of taking fewer policy risks and offering young libertarian activists much less.

Ron Paul has also endorsed fellow Republicans not especially known for their libertarianism. The three-time presidential candidate supported Don Young, the famous pork-barrel spender from Alaska, over a conservative primary challenger in 2008. He backedRalph Hall, a former colleague in the Texas congressional delegation, this year.

Both Pauls have drawn support from networks that include libertarians and more traditional conservative or Republican constituencies alike. For every GOP operator close to Rand, Ron could be linked to someone from the pro-business right-to-work movement or the Christian right.

And some of the differences between the father and son can be explained partly by differing political circumstances. Ron Paul long toiled in relative obscurity, achieving his first mass appeal nationally in his 70s. Rand Paul comes after his father has already won millions of votes in GOP primaries and the conditions seem ripe for expanding that success.

Persuasion is important in politics, but there is a limit to how much a politician can accomplish through education. Rand’s attempt to engage in a philosophical discussion of the trade-offs involved in the Civil Rights Act of 1964, for example, stands as the single biggest political misstep of his still-young political career.

There are benefits and risks to each Paul’s approach. It is honorable to be the lone no vote against unwise or unjust legislation. But that isn’t sufficient to defeat such legislation. To do that, one must be interested in governing and the practical politics that make governing possible. Yet it is possible, even easy, to compromise too much and govern to no particular end other than political self-preservation.

That last concern, even more than whether to endorse Mitt Romney or bomb ISIS, is the real disagreement between Rand and his more libertarian detractors. They believe the senator will end up electing lots of Republican regulars and get devoured by the establishment anyway—or worse, become a Romney himself.

Is it possible to use politics not just to speak truth to power, as Ron Paul did, but to beat the forces of government growth at their own game?

These libertarians say no. Rand Paul thinks the answer is yes.