AMID NEW criticisms about his Senate attendance record, Marco Rubio says some of his rival candidates are getting "a little desperate and a little nasty."

The Florida senator kicked off an Iowa tour yesterday, as a super political action committee backing Jeb Bush announced a new ad in the state accusing Rubio of missing a Senate meeting after the November terrorist attacks in Paris. New Jersey Gov. Chris Christie also piled on during an Iowa stop, questioning Rubio's Senate attendance.

After a town-hall meeting in the leadoff caucus state, Rubio said the ad from Right to Rise "isn't accurate," adding that as a member of the Senate Intelligence Committee he attended a different briefing on the Paris attacks. Asked about Christie's comments, he said the governor had been away from New Jersey "half the time."

"Candidates I think as we get down the stretch here some of them get a little desperate and a little nasty in their attacks," Rubio said.

Rivals have tried to make an issue of Rubio's attendance in the Senate. In 2015, he has missed about 35 percent of roll call votes, according to GovTrack.us. That's more than any of the other senators running for president.

Meanwhile, former New York Gov. George Pataki is telling supporters he's ready to drop his bid for the 2016 Republican presidential nomination.

A centrist Republican who led New York through the Sept. 11, 2001, attacks, Pataki failed to gain traction in a crowded field of candidates during an election season that has so far favored outsiders like billionaire Donald Trump.

Pataki had hung his hopes on doing well in early-voting New Hampshire, but he has barely registered in state or national polls.

He never made it onto a main GOP debate stage, where he would have had the chance to reach millions more viewers, and had trouble raising funds.

Pataki zeroed in on Trump during the undercard debate earlier this month, declaring the New York real estate mogul unfit to be president of the United States.

"Donald Trump is the Know-Nothing candidate of the 21st century and cannot be our nominee," Pataki said.

Pataki told USA Today last month that he would drop out if another candidate who could unite the party emerged. "If someone emerged who I believe could unite the party and lead the country and win the election, then there's no need to run," he said.

Pataki announced his candidacy by video in May.