In endorsing Barack Obama, Colin Powell said he was disappointed and troubled by John McCain's "narrow" campaign approach and the promise of a further "rightward shift" in a McCain administration.

In particular, he cited the choice of Sarah Palin as vice president and the likelihood McCain would name at least two more conservative Supreme Court nominees.

Powell not only gave an insight into his own beliefs but illustrated how McCain has undercut his own candidacy. If he loses, as polls indicate is likely, the principal reason will be the advantage Democrats have enjoyed as a result of this year's poor political climate for Republicans.

But a contributing factor has been McCain's decision to emulate the Bush approach in the two previous elections, with strongly conservative positions and rhetoric.

By going that way, McCain may have sacrificed his single biggest advantage over his GOP primary rivals — his appeal to independents.

With partisans from each party likely to back their candidate, any 2008 Republican nominee needed to win a majority of independent voters. McCain seemed the most likely Republican to do that, thanks to his 2000 campaign against George W. Bush and his independent stances over the years on immigration, climate change, campaign finance and tax cuts.

Last spring, McCain ran even or ahead of Obama among independents. He did so again right after the Republican convention. Now, most polls show Obama leading by 10 points or more among that voter group. Even if that narrows, McCain may find it hard to win in an electorate more Democratic than Republican.

The reasons include his erratic response to the nation's financial crisis and his choice of a hard-line conservative running mate. Sarah Palin has been a detriment with independents, especially women.

If McCain had picked Tom Ridge, he would have sent independent voters a different signal and helped himself in Pennsylvania, although he would have upset some GOP conservatives because the former Pennsylvania governor backs abortion rights.

Picking Palin seemed at odds with McCain's past reputation as someone eager to reach across party ranks. And so has much of his fall campaign, from those robo-calls linking Obama with avowed former terrorist William Ayres to using words like "socialist" and "liberal" to describe the Democratic nominee's policies.

And while McCain has always opposed abortion rights, he used especially fervent language in last week's debate to denounce Obama for saying he would vote to ban late-term abortions only with an exemption for the mother's life or health.

"That's been stretched by the pro-abortion movement in America to mean almost anything," McCain said. "That's the extreme pro-abortion position, quote, health."

In a sense, none of this is new. Since launching his current campaign, McCain has consistently sought to woo the GOP right, endorsing the extension of the Bush tax cuts he once opposed as too big and wooing top evangelical leaders whose influence he assailed in 2000.

Other candidates have done that in contested primaries, both Republicans moving right and Democrats moving left. Most moved back to the center in the general election to woo independents and other less-partisan voters.

Even President Bush did that, at least in tone, in 2000, though he targeted the GOP base in his re-election bid four years later. But he was running when Republicans were riding high so needed less support from independents. Indeed, Bush trailed Democrat John Kerry narrowly among independents in 2004.

This year, Democrats have the advantage.

That makes it even more surprising McCain pursued a course that drove away a Colin Powell and threatens to do the same with other independents who might have elected him.

Carl P. Leubsdorf is Washington bureau chief of the Dallas Morning News. Reach him at cleubsdorf@dallasnews.com.