In South Dakota Sen. John Thune's sprawling debut at this year's Conservative Political Action Committee conference, the potential 2012 Republican presidential contender got specific with some of his complaints about President Obama.

In contrast to former Massachusetts Gov. Mitt Romney, who also sought to present himself as the most credible alternative to Obama for the GOP, Thune pounded the Obama administration on a slew of specific issues, whereas Romney presented a more sweeping difference in vision.

Thune blasted "ObamaCare" and the Federal Communications Commission under Obama for "trying to regulate the Internet." He also criticized the EPA's maneuvers following the failure of cap-and-trade in Congress as well as the National Labor Relations Board for trying to act in light of the failure to pass card check.

Thune urged the adoption of "a two-year budget that spends money in the odd-numbered years and saves money in the even-numbered years, when folks go home to run for re-election," and he ticked off several specific issues Congress is working on, whereas Romney offered more holistic themes.

The contrast is an important one as Thune struggles with whether or not to make a presidential run now.

Neither Romney nor Thune took questions after their speech, but their entrances to the conference couldn't have been more different.

Thune entered through the front lobby, shaking hands and meeting new faces. There was less scrutiny and less attention on his appearance. Romney was ushered in for his speech and kept the press waiting while he escaped to a post-speech reception.

Romney is well-known to the GOP electorate after his first bid for the presidency in the last cycle; Thune, who has been ascending Republican Senate leadership, is a new face.

What's more, while Romney avoided talking about the Republican Party and its players, Thune took a slightly different approach.

He presented himself as a contrast to Obama, but he also tried to mix it up a little with the field.

He poked at potential Republican primary competitors Romney, former Minnesota Gov. Tim Pawlenty and former Alaska Gov. Sarah Palin right off the bat, reminding the audience, "I've never had a book signing. I've been to Iowa plenty of times, but it's usually on my way to South Dakota. And the closest I've come to being on a reality show is CSPAN's live coverage of the Senate floor. "

Romney just re-released his book, "No Apology," last week and has been promoting it. Pawlenty recently released a book, "Courage to Stand," and has been barnstorming Iowa already. Palin stars in a show about her life in Alaska on TLC.

Thune pointed out that he has been spending his time working for his constituents. He later mentioned that he sat next to Democratic Sens. Tom Carper of Delaware and Kirsten Gillibrand of New York during the State of the Union address and joked, "Apparently it takes two Democrats to balance me out."

Advisers explained that Thune's presentation was meant to suggest he is the most conservative option to Obama who is also electable.

As Romney continues to plug his wife's eagerness to have him run for president in 2012, Thune promoted his wife, Kimberley, at both the open and close of the speech.

Near the end of his speech, he discussed his unsuccessful bid to unseat Democratic Sen. Tim Johnson in 2002 and successful second attempt at a Senate seat in 2004 when he ousted then-Majority Leader Tom Daschle.

"I'll never forget what my wife said the day we decided to run," he said. "She said, ‘I finally concluded and realized that what we went through in that Senate race in 2002 wasn't just about the winning. It was about being in the race.'"

"What?" he improvised, to laughs.

He continued, "I thought that was a pretty profound observation, because, for me, it's always about winning. I'm a competitor and I'm in it to win it. But she was saying that - win or lose - it's important to be in the arena. It's important to be out there and fighting for what we believe in. She was right then, and she's right now."

Some Republicans have speculated over the past year that Thune may need to run in 2012 in order to have a good shot at the presidency in future cycles if he is not successful now. And toward the end of his remarks, he warned, "We may not win every battle every time," but he urged the crowd to "have the courage to continue our fight" and "make 2012 our moment."

If Thune chooses not to run for president, advisers say he will look at the race for GOP whip now open after Arizona Sen. Jon Kyl announced his decision Thursday not to seek re-election, but for now he's still torn. Just as he was preparing to deliver his remarks, a loud "run, John, run" chant came from several young attendees in the audience.

And asked by RealClearPolitics this week what reporters should be writing about him these days, he joked, "Just make it up as you go along."

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