NATIONAL HARBOR, Md. — Sen. Marco Rubio steered well clear of immigration reform in his speech to a gathering of conservative activists at the annual Conservative Political Action Conference, opting to stick to bread-and-butter attacks on climate change and marriage equality.

Rubio's decision to not mention immigration reform is particularly remarkable given the fact that it has become a central part of his work in the Senate.

But the 2016 presidential aspirant clearly knew his audience: Activists at the CPAC conference are generally skeptical of the kind of comprehensive immigration reform that Rubio is working on with a bipartisan group of senators.

Instead, Rubio stuck to crowd-pleasing attacks on liberals and a full-throated defense of conservatives.

"Just because I believe states should have the right to define marriage in the traditional way does not make me a bigot," Rubio said to applause, adding, "the people who are actually close-minded in our society are the ones who love to preach about climate science and refuse to believe the science that life begins at conception."