This is shaping up as the "Why not me?" election.

As more candidates declare for president -- three Republicans joined the fray just this week -- they encourage the remaining fence-sitters to take a run more seriously.

Look at John Kasich, now in his second term as governor of Ohio after serving nine terms in Congress. His 23 years in federal public office are almost as many as the six declared candidates combined: former high-tech executive Carly Fiorina, retired neurosurgeon Ben Carson, former Arkansas Gov. Mike Huckabee and three young senators, Ted Cruz, Marco Rubio and Rand Paul.

Kasich has to wake up every morning in the governor's mansion of the nation's most important swing state and tell himself: If they can run for president, I can, too.

Sen. Lindsey Graham of South Carolina is clearly infected by the same virus. After 20 years in Congress, he's a recognized expert on military issues and has probably visited more countries than his potential rivals can even name. "Why not me?" is a question that comes easily to his lips these days.

That phrase, however, only begins to explain a burgeoning Republican field that could eventually reach a dozen or more. The second factor is fragmentation.

Even minor candidates can imagine a twisting path to the nomination in such a crowded field. Suppose Rubio and Paul knock each other out. What if New Jersey Gov. Chris Christie emerges to challenge Jeb Bush for the mainstream vote? Maybe Cruz and Huckabee will fatally wound each other competing for evangelical Christians in Iowa.

The Republican Party has a "royalist" tradition of nominating the next in line. In the 14 elections from 1952 through 2004, the party only once -- in 1964 -- nominated a ticket that did not include someone named Nixon, Dole or Bush. Even the last two nominees, John McCain and Mitt Romney, were very much in the royalist mode.

Yes, there's another Bush running this year, the former Florida governor, and he leads the latest NBC/Wall Street Journal poll with 23 percent of GOP primary voters. But that's hardly an overwhelming lead, and as Bush himself joked recently, "I don't see any coronation coming my way."

A third reason attracting so many candidates is the changing media environment. In the past, notes political analyst Dan Schnur, marginal candidates could not hope to attract much media coverage. "There just wasn't room in the Washington Post for them," he told Politico.

But today, candidates can reach voters directly through social media platforms -- from Twitter and Facebook to YouTube and Instagram. "Even a little bit of media attention is enough oxygen for a race that wouldn't have existed a quarter-century ago," says Schnur.

Add a fourth reason: Supreme Court decisions that have enabled wealthy donors to back individual candidates through independent super PACs. In the last cycle, former House Speaker Newt Gingrich was kept afloat by one donor, casino billionaire Sheldon Adelson, and many of this year's hopefuls yearn for an Adelson-like angel to fund their fantasies.

There's a fifth reason why so many Republicans are considering the race: the widening cracks in Hillary Clinton's candidacy. A torrent of bad news, from lost emails to secret donations, has clearly damaged her reputation. In the Wall Street Journal poll, her negatives jumped from 36 percent to 42 percent in just one month.

More seriously, only 1 in 4 voters views her as honest and straightforward. She stills beats her main GOP rivals in head-to-head match-ups, but her margin over Paul is only three points, and over Jeb Bush, it's six. Suddenly, the GOP nomination seems a lot more valuable.

History teaches a sixth lesson. The last three Democratic presidents-- Jimmy Carter, Bill Clinton and Barack Obama -- were all outsiders when they ran. None of them waited their turn or deferred to their elders. Clearly many younger Republican hopefuls have learned from their example: Take a chance. It might not come around again.

Of course, not all of the GOP candidates actually believe they can win the nomination. Some, like Fiorina, might be angling for vice president. Others might be hoping to raise their profiles and fill their pockets.

Huckabee, after all, cashed in after his failed run in 2008 by securing lucrative TV, book and speech deals. He even did a cheesy diabetes infomercial.

But no matter what their secret dreams or hidden motives might be, a boat-load of Republicans are all asking the same question right now.

Why not me?