According to a top aide, John McCain recently endorsed George W. Bush’s right to wiretap American citizens without court approval, despite the clear requirements of the Foreign Intelligence Surveillance Act (FISA). Clearly, McCain has learned nothing from the past seven-plus years of Bush/Cheney assaults on the Constitution.

More troubling is that he doesn’t seem very worried that his position will generate serious criticism. And apparently it has not. The lack of public outcry points to the likelihood that too many Americans are either confused about a President’s prerogatives or have been persuaded by the years of Bush’s constitutional abuses that a chief executive has the right to violate the law or subvert the Constitution in other ways.

McCain’s position and the response to it demonstrate how much the Bush Administration has damaged public understanding of the system of checks and balances that lies at the heart of our democracy. The framers believed that unchecked power, including unchecked executive power, was the greatest threat to our liberties, but too many citizens today perceive that danger as unreal.

That is why Congress should initiate impeachment proceedings now.

Impeachment is one of the few ways Congress can draw limits around presidential power and educate the country about those limits. And without the people’s support for those limits, they will be breached again and again by future Presidents.

The proposed revisions of FISA that recently passed the House give added urgency to the impeachment argument. Some Democrats have announced support for the bill because they believe it will restrain this and future Presidents. The bill provides that FISA is the exclusive means by which a President may authorize wiretapping. But the original FISA bill had a similar provision, and it did not stop Bush from repeatedly claiming that as commander in chief he has the authority to ignore FISA.

Impeachment is the only way to force a President who steadfastly refuses to obey the law to do so. And it sends an indelible message to future Presidents as well.

We know that the impeachment process, done properly, without partisan rancor and with fairness to the President, can have a hugely positive effect on public understanding of the Constitution and strengthen the democratic underpinnings of the society. This is what happened during the impeachment process against Richard Nixon. We learned that impeachment is not just a grand inquest or inquisitorial process; it is also a great teach-in–a unique opportunity for an extended and serious national discussion of checks and balances, the limits on presidential power and how to preserve our liberties.

Take illegal wiretapping by a President. One of the grounds for impeachment in the House Judiciary Committee’s resolution was Nixon’s illegal wiretapping of journalists and White House staffers. After that resolution passed with bipartisan support, and after Nixon resigned rather than face certain impeachment and removal from office by the whole Congress, an understanding that national security wiretaps had to be carried out in accordance with the law and the Constitution continued for a quarter-century, until Bush’s sledgehammer shattered it. In theory, a Supreme Court case might re-establish checks on the presidency, as the cases regarding the Guantánamo detainees have begun to do. But challenges to some of the most serious abuses of presidential power–wiretapping in violation of FISA, the mistreatment or torture of detainees, signing statements, by which the President claimed he was not bound to obey the bills he signed into law–might never be heard by the Court. An impeachment inquiry would resolve those challenges.

It would also permit Congress to delve into other matters, including the President’s role in outing Valerie Plame and the US Attorneys scandal, that involve possible serious abuses of power that may not otherwise be fully investigated. Bush stalls Congressional inquiries with extreme claims of executive privilege, but there is no executive privilege in an impeachment inquiry, a precedent created during the Nixon impeachment process. And without impeachment, it is hard to envision any other way of holding President Bush accountable for the deceptions, exaggerations and misstatements that drove the United States into the tragic war on Iraq.

While some may argue that impeachment would divide the country, create sympathy for Bush and thus lose the presidential election for the Democrats, that need not be the case. The Nixon impeachment not only resulted in a rout of the Republicans in November; it brought Americans together as they rediscovered a shared basic value, namely, that more important than any individual or party was the rule of law itself. That process educated Congress and the country. It can again.

Finally, it is not essential to finish the entire process of impeachment in the House and trial in the Senate in the few remaining months of this Congress. In the words of the Talmud: you are not required to finish the task, but neither are you free to desist from it. There will not be another opportunity to hold this President accountable in this way; and if we do not act, the signal to future generations is that impeachment, a weapon intended to defend the rule of law, has grown rusty and unusable on our watch.