(CNN) - Sen. Rand Paul criticized New Jersey Gov. Chris Christie's decision to expand Medicaid in the state, calling the decision "very expensive and not fiscally conservative."
The first-term Republican senator from Kentucky said that while no “one person gets to decide what is and what isn't conservative,” the New Jersey governor’s acceptance of a portion of President Barack Obama’s Affordable Care Act suggests that Christie is not a true conservative.
"On the case of the New Jersey governor, I think embracing Obamacare (and) expanding Medicaid in his state is very expensive and not fiscally conservative - and really, many Republican governors who I would say are conservative did resist expanding and accepting Obamacare in their states," Paul said, appearing on CNN's Erin Burnett OutFront on Tuesday.
Paul continued: "That fact, I would say, would lead towards you making the conclusion that it's not a very conservative proposal."
Both Paul and Christie are considered likely Republican contenders in the 2016 presidential race.
In February, Christie became the eighth Republican governor to accept the expansion of Medicaid included in the Affordable Care Act, explaining to skeptics that refusing the federal dollars would put other states ahead of his own.
"I am no fan of the Affordable Care Act," Christie said. "I think it's wrong for New Jersey and wrong for America. I fought against it, and believe in the long run, it will not achieve what it promises. However, it is now the law of the land."
In June 2012, the Supreme Court upheld the individual mandate of Obama sweeping health care law and the Medicaid expansion, though it allowed states to choose whether to participate in the expansion program.
Paul's questioning of Christie's conservative chops hasn't let up over the past couple weeks.
Christie won re-election earlier this month, garnering broad support in the historically blue state of New Jersey. After criticism from members of his own party, such as Paul and Sen. Marco Rubio, R-Florida, who is also considered a potential presidential candidate in 2016, the Garden State Republican said he doesn't feel he has any "fence-mending" to do with the GOP.
"I am going to be me. And if I ever decide to run for anything again, if being me isn't good enough, then fine, I will go home. This isn't my whole life," he said at an event in Washington on Monday.
CNN's Dan Merica contributed to this report.