Tuesday night’s Republican National Convention session demonstrated how the beleaguered GOP still hopes to win in November with John McCain.

In a vacuum, the speeches by Sen. Joe Lieberman and former Sen. Fred Thompson about McCain’s courage and independence were great.

Last week, Democrats portrayed McCain as a George Bush dupe, with no answers for the economy, health care, or an unpopular war in Iraq. As MSNBC’s Chris Matthews put it Tuesday, Republicans had to change the subject: “The only strength they have that’s real is the heroic history of John McCain.”

Thompson was terrific, much better, livelier and more emotional than when he was running for president himself.

He spoke of McCain’s suffering and tenacity when the Navy aviator spent five and a half years as a POW in Vietnam. His plane was slammed by a missile and, as he ejected, he broke his arms, a leg and a knee:

“An angry mob got to him when he fell to the ground. A rifle butt broke his shoulder. A bayonet pierced his ankle and his groin. They took him to the Hanoi Hilton, where he lapsed in and out of consciousness for days. He was offered medical care for his injuries if he would give up military information in return.

“John McCain said, ‘No.’ ”

He developed a high fever, lost weight and was placed in solitary confinement. Thompson spoke of “isolation, incredible heat beating on a tin roof, a light bulb in his cell burning 24 hours a day, boarded-up cell windows blocking any breath of fresh air.”

And: “The guards cracked ribs, broke teeth off at their gums. They cinched a rope around his arms and painfully drew back his shoulders…”

Today, Thompson said, “John McCain can’t raise his arms above his shoulders. He can’t salute the flag of the country for which he sacrificed so much … We salute him.”

TV showed delegates mesmerized, biting lips, fighting tears. I too almost cried. “Great story,” I wrote on my pad. “But nothing to counter Dems re jobs, health care, home foreclosures etc.”

In its own way, the speech by Lieberman, the 2000 Democratic vice presidential nominee, who was reelected to the Senate in 2006 as an independent and who caucuses with the Democrats, also was riveting.

“Country matters more than party,” said Lieberman, a personal friend of McCain, whom he pictured as a strong-willed, free-spirited maverick willing to tackle tough issues such as campaign finance and immigration:

“God only made one John McCain, and he is his own man.”

I like it! Except, um, earlier this same evening, McCain was extolled by President Bush, who addressed the convention by satellite and especially cited the Arizonan’s support for the Iraq war.

Also, while I revere McCain’s military service and credit him with legislative battles he has waged against, say, tobacco, his political courage seems episodic. Most specifically and recently, he tapped the little known, inexperienced Alaska Gov. Sarah Palin to run for vice president. Sure, you can credit McCain for taking a chance to alter the race.

Tempering this, though, is the knowledge that McCain really preferred the pro-choice Lieberman (or former Pennsylvania Gov. Tom Ridge) but had to back down in face of a prospective convention revolt by anti-abortion forces.

Had McCain stood up to them and insisted on Lieberman or Ridge, I would have been really impressed.

But he didn’t.

M. Charles Bakst is The Journal’s political columnist.

mbakst@projo.com