Republican presidential candidate Rand Paul took a heavy swipe at rival Sen. Marco Rubio (Fla.) on missing key votes in the Senate, joining critics who have accused Rubio of failing to do his day job as he shores up support for his White House bid.

“The difference between Marco Rubio and I is I show up for work. He’s missed about a third to a half of his votes this year,” Paul (Ky.) said on CNN’s “State of the Union” on Sunday. “We have the biggest vote of the whole year, voting on a trillion dollars' worth of spending, and he didn’t show up.”

Rubio met with criticism for missing a vote on an important $1.1 trillion spending bill and tax package on Friday. The senator, who has been frequently criticized for his attendance record, initially indicated that he would be on Capitol Hill attempting to slow down the legislation.

“Yeah, I think he ought to resign or give his pay back,” Paul added, echoing statements he made about Rubio’s absence on Friday.

Rubio responded in an interview with CBS by criticizing the Kentucky Republican for running for reelection to the Senate at the same time that he is running for president.

"Here's the other point about Senator Paul, and I don't want to engage him too much because he's got his own style about him,” Rubio said, but “he's the only person running who likes politics so much, he's running for two offices at the same time.”