For my follow-up post on "Obamacans," click here. 

Chuck Hagel (Chip Somodevilla / Getty Images)

Barack Obama is no Chris Rock, but there's one story he likes to tell on the trail that always makes me laugh. According to the Democratic nominee, there's a particular breed of Obamaniacs who approach him after events to confess their Obamania--sotto voce. “They whisper to me," he says. "They say, ‘Barack, I’m a Republican, but I support you.’ And I say, ‘Thank you.'" Pause. Blink. Blink again. And then: "'Why are we whispering?’” It's all in the delivery.

I bring this up today because they're no longer whispering. As we speak/type/read, the Obama camp is holding a conference call with reporters to unveil "Republicans for Obama," a branch of its operation designed to show that "Republicans are coming together in support of Senator Obama to bring change to Washington." That claim was verifiable during the early Democratic primaries, when Republicans willing to crossover and vote in the Democratic contests typically backed Obama over Hillary Clinton by overwhelming margins. Which is why Obama began telling his Obamacan tale in the first place. But now that he's vying for Republican support against a real, live Republican--a slightly different dynamic--I started to wonder whether the story would still hold up to scrutiny.* Obama may count prominent GOPers like Nebraska Sen. Chuck Hagel, presidential granddaughter Susan Eisenhower, Fairbanks, Alaska Mayor Jim Whitaker, former Iowa Rep. Jim Leach, former Rhode Island Sen. Lincoln Chaffee and former White House intelligence adviser Rita E. Hauser--all of them namechecked on today's call--among his announced (or likely) endorsers. But are there enough rank-and-file Republicans whispering their support at Obama rallies to actually make a difference on Election Day?

As I discovered from examination the last 18 months of head-to-head general election polls, the answer seems to be "no." In fact, John McCain's share of the Democratic vote has typically--and surprisingly--been larger than Obama's share of the Republican vote. In other words, it's not that the Rev. Jeremiah Wright scared the Obamacan masses off, as some pundits have theorized--it's that they never existed (in any unprecedented way) to begin with. In December 2006--before the unfamiliar Illinois senator had officially announced his candidacy--McCain attracted 25 support among Dems versus Obama's eight percent among Repubs, according to a FOX News poll**. Those numbers tightened over the next few months of polling by various firms, but Obama never established a sustained lead. A February 2007 Quinnipiac survey showed McCain with 17 percent crossover support, for example, versus nine percent for Obama; in a June 2007 sounding by the same outlet, McCain still led 15 percent to 11. During primary season--between December 2007 and April 2008--McCain's Democratic number typically hovered between 18 and 22. Obama, meanwhile, never climbed higher than 13 percent.

Much of this gap can be attributed to the primary clash with Clinton, whose supporters often said they preferred McCain to Obama in head-to-head polls taken before the final Democratic contests on June 3. But even though McCain's support among Dems declined after Hillary bowed out--a natural result of Democratic unity--Obama's Republican backing didn't budge. Today, Republicans for Obama and Democrats for McCain effectively cancel each other out. The latest numbers from CBS News show Obama at 11 percent crossover support and McCain at 10 (and tied among Independents); FOX News puts the pair at six percent and seven percent, respectively--a result that closely matches where George W. Bush (nine percent crossover) and John Kerry (seven percent crossover) stood at this point in 2004. That also deadlock mirrors 2000, when George W. Bush won over 11 percent of Democratic voters and Al Gore poached eight percent of Republicans--and it means that neither Obama nor McCain, both of whom have repeatedly boasted of their "strong record[s] of bringing people together from the left and the right to solve problems," can currently rely crossover voters to carry them to victory.

I'm not saying Obamacans don't exist. They do. It's just that there's little statistical evidence to support the claim that the number of Republicans who favor this year's Democrat is substantially larger than the number of Republicans who favored his predecessors.

Things could always change, of course. Perhaps over the next 84 days the newly-formed "Republicans for Obama" will add a game-changing number of actual Republican voters to its current roster of Republican politicians. But I'm inclined for now to see it mostly as a publicity effort. With Obama vacationing in Hawaii this week, the major challenge facing Chicago is finding a way to control the news cycle without its candidate's help. "Republicans for Obama" was today's solution--a convenient way to repackage a handful of well-timed GOP endorsements and reinforce the senator's "post-partisan" brand in the process. Whether or not it reflects reality, or has any electoral impact, is probably irrelevant--as long as it transforms a few whispers into a day's worth of headlines.

*Typos corrected.

**FOX is the only firm to consistently break out its results by party affiliation; it has shown Barack Obama leading John McCain overall since June.

UPDATE, August 13: According to new numbers from the Pew Research Center--typically considered one of the nation's most reliable polling firms--the Republican portion of Obama's support base declined from 10 percent to seven percent from June to August, as McCain's Democratic backing grew slightly from 10 to 11 percent. Since June, Obama has established a slight 45-41 lead among Independents--he and McCain were previously tied--but that wasn't enough to prevent an overall net swing of five points for McCain (from 48-40 to 46-43) over the same period of time. As I said before, things can change. But there's still little evidence at this point to suggest that Obamacans (or McCainocrats) will prove decisive in November.