There have been two indispensable men in the U.S. Senate when it has come to national security, human rights and the war against jihadist terror. Sen. Joe Lieberman (I-Conn.) is sitting out this presidential election season but Sen. John McCain (R-Ariz.) has been an enthusiastic surrogate for the man who he hopes will defeat his 2008 opponent. McCain has been a constant presence in and outside the Senate on issues ranging from Afghanistan to Iran to defense sequestration.

When he returned to the Republican National Convention, four years after he was the nominee, he was as dogged as ever in defending America’s role in the world. Both vouching for Romney and seeming to encourage him, McCain declared:

At our best, America has led.

We have led by our example, as a shining city on a hill. We have led at the direction of patriots from both parties.

We have led, shoulder to shoulder, with steadfast friends and allies. We have led by giving voice to the voiceless, insisting that every human life has dignity and aiding those brave souls who risk everything to secure the inalienable rights that are endowed to all by our Creator.

We have led with generous hearts, moved by an abiding love of justice, to help others eradicate disease, lift themselves from poverty, live under laws of their own making and determine their own destinies.

We have led, when necessary, with the armed might of freedom’s defenders.

And always we have led from the front, never from behind.

This is what makes America an exceptional nation: It is not just a matter of who we are, it is the record of what we have done.

It is the responsibility that generation after generation of Americans has affirmed and carried forward.

It is the cause that many Americans have sacrificed everything — absolutely everything — to defend.

Plainly, McCain thinks that President Obama has dropped the ball and, in effect, besmirched America’s honor. (“We can’t afford to give governments in Russia and China a veto over how we defend our interests and the progress of our values in the world. We can’t afford to have the security of our nation and those who bravely defend it endangered because their government leaks the secrets of their heroic operations to the media. I believe we can’t afford to substitute a political timetable for a military strategy.”) The contempt for a president he considers a lightweight was not concealed.

McCain traced Obama’s failure to support the Green Revolution and to lead on Syria. (“Sadly, for the lonely voices of dissent in Syria, and Iran, and elsewhere, who feel forgotten in their darkness, and sadly for us, as well, our president is not being true to our values.”)

McCain is no softie when it comes to rooting out waste and excess in the Pentagon. But he knows there are no “cheap hawks,” only effective ones. As Ann Romney vouched for her husband’s heart, McCain vouched for his nerve:

Everywhere I go in the world, people tell me they still have faith in America.

What they want to know is whether we still have faith in ourselves.

I trust that Mitt Romney has that faith, and I trust him to lead us.

I trust him to affirm our nation’s exceptional character and responsibilities.

I trust him to know that our security and economic interests are inextricably tied to the progress of our values.

I trust him to know that if America doesn’t lead, our adversaries will, and the world will grow darker, poorer and much more dangerous.

I trust him to know that an American president always, always, always stands up for the rights, and freedoms, and justice of all people.

I trust Mitt Romney to know that good can triumph over evil, that justice can vanquish tyranny, that love can conquer hate, that the desire for freedom is eternal and universal, and that America is still the best hope of mankind.

Obama will continue to play the Osama bin Laden card, milking his one actual achievement. But McCain showed how vulnerable he can be. In McCain’s telling, Obama has put his own political future above national security interests, let down oppressed people and frittered away our international stature. For McCain this is a fatal character flaw, a matter of honor and credibility.

It is not clear Romney wants to prosecute that case; it’s a good thing McCain is still in fighting form.