As CQ Politics first reported yesterday, former House Intelligence Committee chairman Pete Hoekstra (R-MI) leaked word of his delegation's secret trip to Iraq. Hoekstra, who in 2006 decried "unauthorized disclosures of classified information [which] only help terrorists and our enemies - and put American lives at risk," used Twitter to inadvertently announce the presence of high-ranking American officials in Baghdad.
As it turns out, Pete Hoekstra is just the latest Republican politician to reveal classified national security information in recent years. But unlike Hoekstra, Vice President Dick Cheney, Senator Pat Roberts (R-KS) and House Minority Leader John Boehner (R-OH) leaked their secrets intentionally for the express purpose of aiding their political party and its president.
As CQ related, Hoekstra apparently couldn't resist turning to Twitter to broadcast an OMG moment upon arriving in Baghdad:

A delegation led by House Minority Leader John A. Boehner , R-Ohio, arrived in Iraq earlier today, and because of Rep. Peter Hoekstra , R-Mich., the entire world - or at least Twitter.com readers- now know they're there.
"Just landed in Baghdad," messaged Hoekstra, a former chairman of the Intelligence panel and now the ranking member, who is routinely entrusted to keep some of the nation's most closely guarded secrets.
Before the delegation left Washington, they were advised to keep the trip to themselves for security reasons. A few media outlets, including Congressional Quarterly, learned about it, but agreed not to disclose anything until the delegation had left Iraq.

Of course, Hoekstra's traveling companion John Boehner knows all about unauthorized disclosures of classified national security information. As Talking Points Memo detailed, in the summer of 2007 the Bush administration was pressing for Congress to codify its regime of illegal NSA domestic surveillance. And at the forefront was Boehner, who warned of a "gap in intelligence" because a FISA court judge had earlier - and secretly - ruled part of the eavesdropping program illegal:

According to the Post, the reason for the administration's feverish effort to get legislation to expand its surveillance powers under FISA is that earlier this year a FISA Court judge declared a key portion of the administration's program illegal. The ruling of course was secret. And it seems that until now the White House had kept this information hidden from Congress.
So why are we finding this out now? Well, that's another interesting story. Minority Leader John Boehner (R-OH) went on Fox News Tuesday night and discussed the whole thing. But the very existence of the ruling is highly classified. So it seems he publicly revealed highly classified information.

Boehner's ploy worked. Despite their majority and support in the law, in August 2007 Congressional Democrats snatched defeat from the jaws of victory by legalizing President Bush's illicit warrantless wiretapping.
As it turns out, Boehner was only trying to match the duplicity of Hoekstra's Senate counterpart, Pat Roberts. Roberts, the long-time chairman of the Senate Intelligence Committee was also a fervent defender of Bush's surveillance program, famously proclaiming, "You really don't have any civil liberties if you're dead." But as the National Journal reported in April 2006, Roberts leaked details regarding Saddam Hussein's whereabouts on March 20, 2003 even as the Iraq war was just getting underway:

"On the eve of the invasion of Iraq, Sen. Pat Roberts was involved in disclosing sensitive intelligence information that, according to four former senior intelligence officers, impaired efforts to capture Saddam Hussein."

Then, of course, there's Dick Cheney and his well-timed PlameGate disclosures. In that politically treacherous summer of 2003, Vice President Cheney authorized the cherry-picked declassification of elements of the 2002 Iraq NIE as part of a campaign to smear Ambassador Joseph Wilson over his public decimation of the White House's uranium in Niger canard. (Americans learned of Cheney's gambit from his former chief-of-staff Scooter Libby, who during grand jury testimony revealed his boss' July 2003 order to leak parts of the NIE.)
For his part, President Bush reflected the Republicans' double-standard on leaking classified information. Asked about the persons responsible for revealing Valerie Plame's identity as a covert CIA operative, Bush on October 7, 2003 shrugged:

"I don't know if we're going to find out the senior administration official. Now, this is a large administration, and there's a lot of senior officials. I don't have any idea. I'd like to. I want to know the truth. That's why I've instructed this staff of mine to cooperate fully with the investigators -- full disclosure, everything we know the investigators will find out."

Two years later, however, a furious President Bush thundered against the New York Times for its December 2005 disclosure of the NSA domestic spying program, which he deemed "a shameful act" that is "helping the enemy." Under Alberto Gonzales, the Bush Department of Justice launched an investigation, which ultimately led to former DOJ official Thomas Tamm as one of the paper's leak sources. (While conservatives no doubt will continue to call for the prosecution of both Tamm and the New York Times, the Obama administration will likely pursue neither.)
Meanwhile, Pete Hoekstra seems to be enjoying his excellent adventure in Iraq. ("Moved into green zone by helicopter Iraqi flag now over palace," he twittered, "Headed to new US embassy.") But as his boneheaded instant message from Mesopotamia suggests, a leak apparently isn't a leak if a Republican does it.