Ted Cruz is siphoning off Rand Paul supporters. (Photo by Drew Angerer/Getty Images)

For months, the presidential campaign of Sen. Ted Cruz (R-Tex.) has quietly been courting libertarian-leaning supporters -- people who once supported Ron Paul and ostensibly would have been inclined to back his son, Sen. Rand Paul (R-Ky.) in the 2016 race.

On Tuesday, Cruz released a video showing eight former Ron Paul liberty movement supporters -- a number of them from Iowa -- who are now backing Cruz. The campaign announced that former Congressman Bob Barr will chair a Liberty Leaders for Cruz" coalition comprised of libertarian-leaning Republicans.

As Paul's campaign has floundered and Cruz remains in the middle of the pack, Cruz's campaign has made the case to Paul supporters that the Texas Republican can remain in the race for a long time -- and that while he does, he will espouse libertarian principles. At rallies this summer, Cruz has evoked the Fourth Amendment, railed against the Fed and talked about his efforts to end the bulk government collection of metadata.

In the video, Cruz's supporters talk about how both Pauls endorsed Cruz's 2012 Senate run and said they believe he has held positions consistent with the liberty movement, including a reluctance to send boots on the ground to Syria and support for Rand Paul's bill calling for an audit of the Fed.

"He's really picked up the mantle of Ron Paul in many ways," Joel Kurtinitis, a co-founder of Liberty Iowa and Ron Paul's 2012 regional director, says in the video.

Cruz's team has compared the GOP presidential campaign to an NCAA basketball bracket, with the field divided into conservative, evangelical, libertarian and establishment voters. Cruz's team has been doggedly pursuing conservatives and evangelicals, holding a religious liberty rally in Iowa last month and taking the lead in a fight over funding Planned Parenthood.

Cruz's team has quietly worked to tap into the liberty movement in lower-profile ways as well, sending an adviser to New Hampshire to woo both current Rand Paul and former Ron Paul supporters.

In a statement, Barr said that Cruz understands the oath of office is a "solemn commitment" to act in accordance with the Constitution.

"Which is after all, the mechanism whereby our individual and collective freedoms as a country are secured. It is that commitment to the Constitution and to Liberty that has drawn me to serve Sen. Cruz,” Barr said.

James Hohmann and David Weigel contributed reporting.