Newark Mayor Cory Booker again clarified comments he made about President Barack Obama's attacks on Mitt Romney's private sector record, stating that he was "upset" by Republicans "manipulating" his words.

Booker, who set off a political firestorm on Sunday's "Meet The Press" when he called criticism of Romney's time at private equity firm Bain Capital "nauseating," told MSNBC's Rachel Maddow that he felt "used" by the Republican National Committee, which on Monday launched a petition encouraging Americans to "stand with Cory."

"I'm very upset I'm being used by the GOP this way," Booker said during the Monday interview with Maddow, expressing that he and his staff were particularly angered by the RNC claiming that it stands with him.

"I have not seen a Republican national candidate be willing to stand with me in places like Newark, Camden," Booker said.

He continued: "People have ignored Newark before, but to exploit it or its mayor -- that's something I'm not going to sit still for."

Booker also denied the RNC's suggestion that he had been coerced by the Obama campaign into walking back his eyebrow-raising statements in a YouTube video released Sunday evening.

"They never pressured me to do anything," Booker said. "I certainly did talk with campaign officials, but they didn't force me to do anything."

He also added that while both sides are guilty of the type of negative attack ads he said his "Meet The Press" comments were meant to indict, he said he feels the GOP often goes too far.

"You can't even equate the negativity on the right with what's happening in some sectors on the left," he said.

Following the interview, Booker sent a series of tweets using the hashtag "#IStandWithObama":

Let me be clear, #IStandWithObama — Cory Booker (@CoryBooker) May 22, 2012

If you stand w/ me you would stand 4 health care that doesn’t try to turn the clock back on women #IStandWithObama — Cory Booker (@CoryBooker) May 22, 2012

If you stand with me you would stand for marriage equality #IStandWithObama — Cory Booker (@CoryBooker) May 22, 2012

Below, Obama surrogates to keep an eye on this election cycle.

PHOTO GALLERY Obama Surrogates