Finish what you start. That’s an admirable concept.

It’s also a traditional theme from possible vice-presidential picks proclaiming their resolves to stay on the jobs they already have.

As Indiana Gov. Mitch Daniels, asked if he would accept an offer to be Mitt Romney’s running mate, phrased it a week ago on “Fox News Sunday”: “I promised the people of my state eight full years, and I like living up to that commitment, showing that it was real.”

Sound familiar? Early this month, our Gov. Nikki Haley used some of the same wording on ABC’s “Nightline”: “I made a promise to the people of this state. And I think that promise matters. And I intend to keep it.”

Hey, politicians — and the rest of us — should keep our promises.

But at some point, shouldn’t some of the politicians touted as promising VP material concede that they’re clearly not?

Haley has been governor for less than 16 months, and before that was a member of the S.C. House for a mere three terms. Despite her high national profile, she’s already had some low points as our state’s chief executive.

Romney should learn from the losing experience of John McCain, whose 2008 running mate had been governor of Alaska for a mere two years.

No, Sarah Palin didn’t cost McCain the White House.

Yet Palin’s spunk can’t erase her at least partially earned goofball image. That made lots of Americans — and not just Democrats — nervous about her becoming our backup for a president who would have turned 73 seven months after being sworn in.

OK, so the words “President Joe Biden” aren’t exactly reassuring, either.

And Barack Obama’s pre-presidential resume was mighty thin, too — “community organizier,” law professor, eight years in the Illinois Senate, four in the U.S. Senate.

At least George W. Bush had been governor of a large state for six years before becoming president. Before that, he was an oil-biz bust, then a profitable part-owner of the Texas Rangers (the baseball team, not the law-enforcement agency of Cordell Walker fame). Before that, he got an Ivy League education — a bachelor’s degree from Yale and an MBA from Harvard.

Yes, Obama has an Ivy League degree, too — from Harvard Law School.

Back to the backup plan for Romney, who graduated from both Harvard’s law and business schools: If he wants a running mate from our Palmetto State, both of our U.S. senators would bring more impressive credentials than Haley to the ticket.

Yet Jim DeMint, now in his second term as our junior senator after three U.S. House terms, sounded refreshingly humble last August with this response to speculation about him running for the White House: “I think I’m the only senator who does not see a president when I look in the mirror.”

And Americans should see potential — and abruptly promoted — presidents when they look at vice presidents.

Of course, the ultimate qualification for any presidential ticket is the ability to garner 270 electoral votes. But the importance of choosing the right No. 2 extends beyond his — or her — impact on that political challenge.

Ponder the presidencies of the last three veeps who suddenly moved up:

¦ Harry Truman: Finished the World War II job with gutsy call to nuke Japan. Won upset 1948 election against last mustachioed major-party nominee (Thomas Dewey). Left door open for communist North Korea’s invasion of South Korea, then put U.S. at the front of U.N. “police action” to save our ally. So unpopular by 1952 he didn’t seek another term.

¦ Lyndon B. Johnson: Muscled overdue Civil Rights Act through Congress. Muscled overextending “Great Society” programs through Congress, launching costly “War on Poverty” we can’t win. Rolled to 1964 landslide while warning that Barry Goldwater would get us into a land war in Vietnam. So unpopular by 1968 he didn’t seek another term.

¦ Gerald Ford: Helped reunite divided nation. Though his “WIN” (Whip Inflation Now) buttons didn’t work, nearly won 1976 election despite unpopular but wise call to pardon Richard Nixon.

Perhaps you disagree with those astute presidential assessments.

Still, there’s no debating that vice presidents must be ready to step up in a hurry.

And lest you doubt my qualifications, this newspaperman also has a degree from a highly esteemed bastion of learning — Clemson University.

Then again, so does Haley. Frank Wooten is assistant editor of The Post and Courier. His email is wooten@postandcourier.com.