A year before the 2012 primary, the Republican race for U.S. Senate is running fast and furious.

Whipped on by the social media site Twitter, the campaign took a defining turn this week over the issue of U.S. Rep. Paul Ryan's Medicare plan.

Jostling with Mike Haridopolos and George LeMieux for the right to take on Democratic Sen. Bill Nelson, Adam Hasner jumped on Haridopolos' failure to clearly support or oppose the Ryan plan.

Tweeting and retweeting comments about a North Florida radio talk-show host booting Haridopolos off the air, Hasner's senior adviser Rick Wilson created an instant talking point for the campaign. The not-so-subtle message: "Real" conservatives, like Hasner, back Ryan's Medicare reform proposal.

Within hours, Haridopolos announced he, too, supported Ryan. Then LeMieux jumped in to say he was on board as well.

The whole sequence of events spanned less than a single day, but the impact could make a lasting impression on the high-profile race.

At this stage, each candidate is striving to grab the attention of dedicated GOP voters and energize party activists -- and social media outlets like Twitter and Facebook are increasingly becoming the tools of engagement.

"Twitter is an important audience for the primary. It flies under radar for mainstream media," says Kevin Wagner, a political science professor at Florida Atlantic University.

As the Medicare story illustrated, Twitter wars will spill onto the pages of the mainstream press, and Hasner clearly benefited from Wilson's aggressive tactics. By putting Haridopolos and LeMieux on the defensive, Wilson almost instantaneously framed his candidate as the "true conservative" in the race.

And in a sign of grudging respect (or electoral fear), liberal tweeters from Progress Florida and Think Progress even piled on to tweak Haridopolos.

Because GOP primary voters are more conservative than the electorate at large, Republican primary candidates seek to claim their niche on the right.

"Haridopolos has a lot of institutional [party] support behind him, he's in a significant position. Hasner is starting from farther out. He has nothing to lose," Wagner observed.

Yet short-term gain can result in long-term pain for candidates who define themselves too tightly. Hard-line positions that play well in primary battles can backfire during general elections, especially in a purple state like Florida.

While tea party and disestablishment conservatives tar middle-of-the road Republicans with the pejorative RINO (Republican in Name Only), pragmatic party members warn of the EIPO (Electable in Primary Only).

Somehow the GOP hopefuls must avoid either label.

"LeMieux is the best general-election candidate because he has cross-party appeal, but he's the worst primary candidate," Wagner opined.

Daniel Smith, a political science professor at the University of Florida, observed "an amazing amount of waffling by Haridopolos" on the Ryan-Medicare issue, which Smith calls a "litmus test" for Republicans.

"His last equivocation -- that he supports the plan, but not certain provisions -- won't wash well with Republicans," Smith predicted.

Indeed, all nuance is lost amid Twitter tweets that are limited to 140 characters. In this high-tech headline service, sharp attacks can go viral before an effective response can be aired.

Robin Stublen, a tea party leader from Charlotte County, believes Haridopolos has already "lost the tea party vote."

"His game-playing on illegal alien legislation and his support for SunRail all suggest that he has a lot to learn about true fiscal conservatism," Stublen said.

But Stublen, like many tea party activists interviewed for this article, is yet to be enthused by the rest of the GOP field.

"I see no electable conservative in the U.S. Senate race. I, for one, am tired of holding my nose and voting," he said.