John McCain often performs best when acknowledging his own errors, and so he began his remarks at the Greater Columbus Convention Center last week. The Arizona senator and Republican presidential nominee accepted his share of the blame (along with his fellow pols and the media) for the soundbite culture of campaigns.

He explained that amid the photo ops and the barrages of accusations, all spun through the 24-hour news cycle, ''voters . . . can be forgiven their uncertainty about what the candidates actually hope to achieve if they have the extraordinary privilege of being elected president of the United States.'' He wanted to bring a moment of clarity, ''to describe what I would hope to have achieved at the end of my first term as president.''

Notice that word ''hope''?

McCain presented much to admire in his address, in particular, the departure in tone and approach from the current resident of the White House. Yet reading the speech, three words came to mind: Yes we can.

The senator reminded early that ''I cannot guarantee I will have achieved these things.'' He then proceeded to tell the story of a presidency that addresses, in larger and smaller ways, practically every national ill.

And Barack Obama talks grandly about remaking the capital and the country? McCain portrayed an almost breathtaking set of accomplishments. The news accounts have focused on the winning of the Iraq War, Iraq becoming ''a functioning democracy,'' Osama bin Laden captured or killed, Iran and North Korea abandoning their nuclear ambitions, even the financial ''fix'' for Medicare and Social Security. That isn't a sliver of the advances.

Consider the rescue of Dafur by ''a newly formed League of Democracies,'' or taxpayers having a choice: file under ''the current complicated and burdensome tax code or use a new, simpler, fairer, flatter tax, with two rates and a generous deduction.''

Then there is the end of ''unneeded farm subsidies,'' test scores and graduation rates ''rising everywhere,'' obesity among the young ''beginning to decline.'' And more: The country is ''well on the way to independence from foreign sources of oil. . . . Illegal immigration has been finally brought under control. . . . Scores of accomplished private sector leaders have joined the ranks of my administration for a dollar a year and have instituted some of the most innovative reforms of government programs ever known.''

One passage (hitting close to home) captures just how ambitiously (or loosely) McCain is thinking. He first envisions ''Americans, who through no fault of their own, lost jobs in the global economy they once believed were theirs for life'' assisted by improved unemployment insurance and worker retraining. By the end of the paragraph, he sees those workers finding new jobs ''that won't go away.''

Splendid. Anyone opposed to the bulk of these and other advances, a less threatening world, a more prosperous economy, better report cards?

This isn't a bid to discourage candidates from plunging into the vision thing. The better candidates articulate clearly where they want to take the country. Hard to resist McCain, among other things, eschewing signing statements, pledging an end to the permanent campaign, embracing the job of combating climate change, reshaping a middle way on immigration reform. The worry involves a twist on the ''voter uncertainty'' he discussed.

Might a voter wonder in view of all of these intended achievements on so many fronts: What matters most to McCain? Priorities, please?

Yes we can do what, precisely, a Republican president having to contend with a Democratic Congress?

This speech signaled much about McCain positioning himself for the fall campaign, upbeat, independent, the maverick at work. Yet that element of fuzziness provided a different reminder. The senator doesn't always talk as straight as he would like you to believe.

Take the section about the Iraq War. McCain has been cudgeled (unfairly) for his comment about remaining in Iraq for 100 years. At the same time, he has been adamant about resisting a timetable for withdrawal. Now he floats the year 2013 for mission mostly accomplished in this unpopular war, the five-year timeline softening the edge of his previous stance, a deadline but not deadline.

McCain talks tough about confronting Hamas as part of pursuing a peace settlement between Israelis and Palestinians. He suggests that Hamas has ''endorsed'' Barack Obama. Would the Democrat proved naive in battling terrorism? Engage Hamas?

Jamie Rubin surfaced last week on CNN and in the Washington Post. The former State Department official in the Clinton years (now a journalist type) replayed his 2006 interview with McCain, the senator caught on videotape explaining about Hamas: ''They're the government. Sooner or later, we are going to have to deal with them, one way or another . . . it's a new reality in the Middle East.''

Much has been made about McCain opposing the Bush tax cuts seven years ago, and now calling for their permanent extension. This latest posture collides with the image he cultivates of McCain the deficit hawk. He fumes about earmarks, yet the savings would not begin to cover the elimination of the Alternative Minimum Tax. How would the senator cover the cost?

The task is easy when you share what you ''intend to achieve'' in the White House. Harder is the job of choosing, and in the realm of priorities, not to mention the matter of how, John McCain can be hard to pin down.