Opportunistic politicians are destroying America, Sen. Rand Paul (R-Ky.) said Tuesday in announcing his presidential bid, but he can make things right again.

"We've come to take our country back," he declared, adding that "both parties and the entire political system are to blame."

Which is strange, because in decrying politics as usual, Paul was engaging in precisely the kind of behavior he claims to abhor. Though his speech was rife with the heterodoxy that first vaulted him to prominence — such as calling for an immediate end to domestic NSA snooping — it was equally notable for the ways in which Paul the candidate broke with Paul the ideologue.

This is the central discord underlying Paul's presidential pitch. He's a Washington politician who hates Washington politicians, a self-serving salesman who derides self-serving salesmen. Since stepping onto the national stage five years ago, Paul has cast himself as a steadfast, principled populist. But time and again as he crept toward a White House run, he underwent contrived evolutions to revise past positions — or pretend he never stood for them in the first place.

Of course, Paul is hardly alone in flip-flopping. It's an act as habitual to politicians as shaking hands and kissing babies. But that's precisely the point: Despite projecting an aura of incorruptibility, Paul revealed he, too, will abandon his beliefs when doing so proves politically expedient.

Paul's revisionist history of himself serves two general purposes. On some fronts, he's sought to scrub positions abhorrent to the general public. On others, he's moved to align himself more closely with the Republican base he'll need to win the party's presidential nomination.

In perhaps his most remarkable about-face, Paul said in 2010 that he disagreed with part of the Civil Rights Act barring discrimination by private businesses. Years earlier, he'd made a similar argument, writing that, "A free society will abide unofficial, private discrimination."

Understandably, voicing support for racial discrimination on the flimsy basis of "freedom" did not go over so well, forcing Paul to retreat. And come 2013, while speaking at the historically black Howard University, Paul sought to bury his past position, claiming, "I've never wavered in my support for civil rights or the Civil Rights Act."

Or take vaccines, which Paul claimed earlier this year were in some cases linked to "profound mental disorders." (Hello, Michele Bachmann!) Again, Paul's ideology caused him to run afoul of a significant majority of Americans, and he soon backtracked.

On the other side of the equation, Paul has made a dramatic turn from strenuous anti-interventionist to cautious hawk in hopes of allaying conservative concerns he's weak on foreign policy. But in the process, he's hopelessly muddled his stance on an issue that used to set him apart from the rest of his party

His old budgets called for drastic cuts to defense spending; last month he proposed increasing defense spending. He once insisted on ending all foreign aid, including aid to Israel; last year, as unflinching pro-Israeli support became a required Republican position, he insisted he never "proposed targeting or eliminating any aid to Israel." Before running for office, he said Iran was no threat to the U.S., and as recently as January backed negotiations with Tehran; then in March, he signed a letter along with 46 GOP senators undercutting the Obama administration's ongoing nuclear talks.

Sure, some of Paul's evolution on foreign policy reflects the shifting situation in the Middle East and around the world. But in flailing around for a new position, Paul landed on an identity that stands in diametrical opposition to his old self.

There is a calculating aspect to the timing and degree of Paul's calibrated changes. He's a staunch anti-interventionist who now supports some interventions, a believer in private discrimination except when called out in the press. (It's no wonder he has yet to comment on the religious freedom law brouhahas of the last few weeks.)

Paul knows he cannot win the GOP nomination, nor the White House, without a reboot of Rand 1.0. And that's fine: All politicians engage in doublethink from time to time. It's just that Paul built an identity as the one serious politician too principled to play that game. His disjointed platform and muddled positions suggest otherwise.