Ron Paul is the only Republican presidential candidate not attending the Conservative Political Action Conference this weekend.

While he was asked to speak, he turned down the invitation due to “the travel constraints of his presidential campaign,” according to a press release from the American Conservative Union.

Congressman Paul’s press secretary, Gary Howard, confirmed that they won’t be attending, stating, “We have too much campaigning to do across the country.”

His son, Kentucky Sen. Rand Paul, will be speaking early Thursday evening, and participating in a book signing after.

“While we will miss Congressman Ron Paul, a perennial favorite among our attendees, we are honored to host Sen. Rand Paul, a leader of the next generation of committed constitutional conservatives, at CPAC 2012,” said ACU Chairman Al Cardenas in the press release.

The Texas congressman won CPAC’s presidential straw polls in 2011 and 2010. And while he was won numerous straw polls over the past few months, he still has not won a statewide primary or caucuses in the 2012 GOP presidential contest.