Loyalty to Donald Trump demands more than many people can muster. One Cabinet officer and high-level aide after another has repeatedly endured ill treatment only to finally leave rather than accept further indignities. But no subservience is too much for Mike Pence.

His Wednesday night speech to the Republican National Convention confirmed that the vice president is prepared to say anything to celebrate his boss — and the more absurd the statement, the more resolutely he utters it.

Trump spends hours each day watching TV and posting on Twitter, rarely reads his intelligence briefings, usually doesn't show up in the Oval Office until late morning and plays more golf than a club pro. But Pence gushed, "Few presidents have brought more independence, energy or determination to that office."

Pence would not have accepted the job if he didn't want to be president himself, but his endless prostration before Trump is likely to make it impossible to fulfill that ambition. He has been so emasculated by his boss that Americans and even Republicans will have trouble ever seeing him as anything but a fawning lackey.

He brings to mind Sen. Eugene McCarthy's jibe at Walter Mondale, who, he said, had "the soul of a vice president." In reality, it was Mondale who, under Jimmy Carter, redefined the role as an important adviser and partner, not a fifth wheel.

That has been the template for such successors as Al Gore, Dick Cheney and, yes, Joe Biden. Each brought real skills and experiences that their presidents were wise enough to put to use. Each was therefore able to avoid being fatally diminished by the job.

Pence, by contrast, illustrates the perils of the old-fashioned vice presidency. The first person to hold the office, John Adams, said it meant, "I am nothing, but may be everything." For most of our history, the vice president was the moral equivalent of a spare tire, necessary only in case of an emergency that everyone hoped would never arise.

The scarcity of defined duties, much less powers, made the vice president utterly dependent on his boss. Lyndon Johnson was particularly fond of humiliating Hubert Humphrey, bragging that he had his genitalia "in my pocket."

But Humphrey was complicit in his treatment. After taking office, he said that henceforth, "there is no Humphrey staff, there is no Humphrey program, and there are no Humphrey ideas. From now on, there simply isn't any Humphrey." That posture was a major handicap when he ran for president.

It was not Joe Biden's approach. He agreed to run with Barack Obama on the promise that he would be "the last person in the room" when the president had to make a major decision. He argued his views even when they ruffled feathers. "In the Situation Room," wrote deputy national security adviser Ben Rhodes, "Biden could be something of an unguided missile."

He endorsed same-sex marriage in an interview, before Obama was ready to do so, infuriating some of the president's aides. Biden's response? "I answered as antiseptically as I could. But I was going to sit there and not say what I believe at this point in my career? They can have the goddamn job."

Try to imagine Pence saying that, even without the profanity. Obama may have found Biden annoying at times, but he listened to him, respected him and, late in his presidency, said, "I love that man." Trump exhibits no such regard for Pence.

Should the vice president run in 2024, he would be at a disadvantage against contenders who are in step with Trump on big issues but free to speak for themselves and even part ways with him on occasion. Nikki Haley, Tom Cotton, Marco Rubio and Ted Cruz have never had to be quite as servile in their support. Nor can Pence assume that Trump would repay his loyalty four years from now.

If Biden wins, Kamala Harris would have a boss who knows how useful a vice president can be. "I asked Kamala to be the last voice in the room, to always tell me the truth, which she will, challenge my assumptions if she disagrees, ask the hard questions because that's the way we make the best decisions for the American people," he said. Harris would not be expected to make a daily ritual of swallowing humiliations and spouting lies.

There is a way to serve as vice president without forfeiting your credibility and self-respect. There is also Mike Pence's way.

Steve Chapman blogs at http://www.chicagotribune.com/news/opinion/chapman. Follow him on Twitter @SteveChapman13 or at https://www.facebook.com/stevechapman13. To find out more about Steve Chapman and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.