TAMPA, Fla. -- Former Arkansas Gov. Mike Huckabee served up red meat to Republicans at their national convention, rallying conservatives behind the party’s nominee-in-waiting, Mitt Romney.

Huckabee leaned on standard Republican tropes -- from mocking House Minority Leader Nancy Pelosi and Democratic National Committee Chairwoman Debbie Wasserman-Schultz to decrying "radical left-wing" policies -- in a pitch firmly directed toward the GOP's right wing.

"To those who question how once-rivals can now be united, it’s quite simple -- we have Barack Obama to thank," said the former 2008 presidential candidate, who sparred with Romney in that year's GOP primaries, in a bid to stir conservatives' passions.

Huckabee passed on running for the Republican presidential nomination a second time in 2012, leaving a void in the primary field this cycle for a visible social conservative like this former Southern Baptist preacher.

It was one of the most direct and pointed speeches targeted at President Barack Obama and it riled up delegates as the convention built towards vice presidential nominee Paul Ryan’s acceptance speech Wednesday night. 

"No small differences among us in our party approximate the vast differences between the liberty-limiting, radical left-wing, anti-business, reckless-spending, tax-hiking party of Barack Obama, Harry Reid and Nancy Pelosi, versus an energized America who knows that we can do better," said the former Arkansas governor.

That hard-hitting rhetoric was largely typical of Huckabee's speech, which included jokes about the president's Nobel Peace Prize and Vice President Joe Biden's charitable giving -- along with jabs directed toward a familiar Republican bogeyman, the media.

Huckabee also made reference to his role as a socially conservative leader in an attempt to rally Catholics, a group whom Republicans have courted this cycle, partially by attacking new Obama administration rules about requiring insurers to cover contraception.

"The attack on my Catholic brothers and sisters is an attack on me," he said.

Huckabee made no mention, though, of one of his sharpest differences of late with Republican leaders, over the candidacy of Todd Akin -- the Republican Senate candidate in Missouri whose controversial comments about rape prompted most GOP leaders to call for Akin to end his campaign. Huckabee has stood by and defended Akin.

Slideshow: Republican National Convention

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Republicans gather in Tampa, Florida to officially nominate Mitt Romney and his running mate, Paul Ryan, as the party's candidates for the 2012 presidential election.

Launch slideshow

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Nebraska Sen. Deb Fischer applauds her supporters with her husband Bruce Fischer, left, at her election party May 15 in Lincoln, Neb.

Updated 11:20 p.m. — Insurgent Republican candidate Deb Fischer bested two rivals with superior financing and organizations to win the Republican Senate nomination in Nebraska on Tuesday. 

Fischer earned the right to face former Sen. Bob Kerrey in a Senate race seen as crucial to Republicans' chances of retaking the Senate next year. She and Kerrey will battle to succeed the retiring centrist Democratic Sen. Ben Nelson. 

Fischer bested her two Republican rivals, state Attorney General Jon Bruning and Don Stenberg, according to Associated Press projections. Bruning had enjoyed establishment support and had raised the most money, while Stenberg, who'd previously run for the Senate three times before, had worked to consolidate support from conservatives. 

A state senator who heads the Nebraska legislature's transportation committee, Fischer made a late charge for the nomination aided by a nearly yearlong fight between Bruning and Stenberg. 

Adding to that momentum was former Alaska Gov. Sarah Palin, who on Monday released a letter in support of Fischer.

Romney wins Nebraska primary

“We admire your conservative principles and know that you will not go to Washington to amass great wealth or power. You will go to Washington to serve the people of Nebraska, protect our Constitution and work for common sense solutions to help restore America,” wrote Palin, who made a habit of backing insurgent and Tea Party Senate candidates in 2010, often shortly before Election Day.

Fischer won't face a cakewalk on her way to Washington, though. Democrats tapped former Sen. Bob Kerrey, who served two terms representing Nebraska before becoming president of The New School in New York City, to succeed Nelson.

But Republicans are optimistic that they can paint Kerrey, a Vietnam War hero who unsuccessfully sought the Democratic presidential nomination in 1992, as an out-of-touch liberal. Kerrey, for instance, said last week that he also supports same-sex marriage in light of President Barack Obama’s similar pronouncement – a position that might not prove popular with Nebraskans come November.

Fischer has been the least well-funded of the candidates, and her small organization relative to her two primary challengers could prompt more assistance from the national Republican Party.

Moreover, were Fischer to become Republicans’ candidate, she would be facing statewide exposure for the first time, and against a seasoned political figure like Kerrey.

Republicans' chances of winning the Senate could be diminished, though, if they fail to win over Nebraska. While Democrats will play defense this fall in more Senate seats than the GOP, Republican candidates have struggled to catch fire in some states that had been previously seen as opportunities, narrowing the party's pathway to a majority.

While Fischer's victory would seem at first glance to fall along the fault lines in 2010 Senate primaries, which pitted less-experienced conservative insurgents against establishment-backed Republicans, the three-way primary in Nebraska made for a more complex breakdown in political loyalties. 

Bruning had raised the most money and developed the most extensive organization. Both Rick Santorum, the erstwhile presidential candidate and former Pennsylvania senator, and former Arkansas Gov. Mike Huckabee had endorsed Bruning, giving him particular heft among the state’s social conservatives.

Stenberg, who had hoping the fourth time was a charm in his bid to win a Senate seat, won the backing of Sen. Jim DeMint, R-S.C., a conservative kingmaker in primary races, along with the fiscally conservative Club for Growth.

Both Bruning and Stenberg had been fighting intensely in the GOP primary for much of the past year, aided in part by outside groups who have assisted each candidate.

CHARLESTON, S.C. – The audience at a presidential forum here Saturday booed Newt Gingrich for criticizing Mitt Romney’s record at Bain Capital after Mike Huckabee, the host, told the crowd that candidates would not be allowed to attack each other.

Before the five candidates (Ron Paul was not there) came out one by one for approximately 12 minutes of audience questions, Huckabee explained that they were “not to mention, and not to attack the other candidates.” (The audience, prompted at first by the Huckabee show’s executive producer, clapped and cheered at the directive.)

Gingrich, the third candidate to speak, responded to question about how he could “defend the vilification of companies that are willing to put capital at risk in order to save failing companies” -- a reference to attacks by Gingrich and his super PAC over Romney’s tenure at Bain Capital.

Pushing back on the claim of “vilification,” Gingrich said, “I haven’t done that.”

He began to say he would be visiting the city of Georgetown, which used to be home to a steel mill whose parent company was bought out by Bain in 1993 and went bankrupt in 2001 with more than $500 million in debt according to a Myrtle Beach Sun News account.

“Georgetown has a steel mill. Which was closed. Capital wasn’t put at risk; capital was drained out of that company,” Gingrich said. “Governor Romney ran saying he created 100 thousand jobs in the private sector…”

The audience started booing Gingrich after he said, “Governor Romney.”

Huckabee interrupted Gingrich, saying, “Mr. Speaker, we said we will not allow negative…”

Then Gingrich, retooling, continued, “I’m just trying to answer his question. So let me say it differently.”

“OK,” Huckabee replied.

“I believe that it’s fair to ask the records be clear and that people reveal what happened,” Gingrich said. “But I think to ask questions about a particular company is not the same as attacking capitalism and I don’t see how you can expect us to have a presidential campaign in which an entire sector is avoided."

Several audience members at the forum told NBC News they were displeased at Gingrich’s singling Romney out.

“I think Gingrich lost my respect,” said Janice Shumpert, 57, of West Ashley, who said she was leaning towards Rick Santorum. “It was a bad moment for him. I’m not saying he can’t recover but at this point, I wouldn’t vote for him”

Randy Hinson, 56, of Charleston, said the booing was “appropriate” because “that wasn’t the format.”

“Gingrich actually ruled himself out today for me,” Hinson said. “I guess Romney was at the top for me; I wanted Gingrich, and Gingrich kind of talked himself out of it today.”

Pat Neumann, 58, of Edisto Island, who said she favored Perry, noted the enthusiastic response Huckabee received when he said the forum was to be devoid of negativity.

“We weren’t going to put up with that,” she said of candidate-on-candidate aggression. “It’s going to happen because unfortunately negative campaigning works, and they know it. But people just weren’t going to put up with it today.”

DES MOINES, Iowa – With only 20 days until the Iowa caucuses, four GOP candidates made their pitch to social conservatives tonight at the premiere of an anti-abortion documentary narrated by the former Arkansas Gov. Mike Huckabee.

Michele Bachmann, Newt Gingrich, Rick Perry, and Rick Santorum addressed the 1200 person crowd before the house lights dimmed for the “The Gift of Life” premiere.

“I do want you to take note,” Huckabee told the crowd. “There were four candidates who cleared their schedules, and made this a priority event.”

Former Pennsylvania Sen. Rick Santorum, trailing in Iowa polls, won the biggest applause from the crowd tonight – and aimed his remarks at his competitors.

“I have some problems with some of the folks who running for office these days when they say, ‘I believe life begins at conception.’  That’s like, I say, ‘I believe the sun rises.’” Santorum said, to laughs.

“Why would you say you believe something that’s a fact?” Santorum added. It seemed to be a reference, at least in part, to Gingrich, who spoke minutes earlier in favor of a congressional bill that would define personhood as beginning at conception – though Santorum said later tonight he was talking about a number of his opponents. "I know that there have been several candidates for president who have stated they believe life begins at conception – and as I said, it’s not a belief, its a fact," Santorum told NBC News.

During her remarks, Minnesota Congresswoman Michele Bachmann attacked the Obama administration for considering – before reversing course – making the “Plan B” morning-after pill available on pharmacy shelves, “where little girls could find it next to bubble gum and next to M&M’s."

"President Obama is so tied up in his reelection that even he knew that was one step too far,” Bachmann said. Governor Rick Perry touted his record defunding Planned Parenthood in Texas, where he said 12 clinics have closed as a result. He called the new film a tactic in the fight against abortion, saying, “imagine the difference you can make not in just one life, but in two.”

Attacks on Gingrich awaited people after the movie premiere.  A group billed as "Iowans for Life" paid for fliers on cars that read, "The bottom line: Newt Gingrich is a pro-life fraud."

But as Huckabee pointed out during his short remarks inside the theater: “I think it is significant that all four of the candidates who are present tonight have endorsed life. And that ought to be very important.”