The national poll, which does not reflect the Electoral College or prioritize the swing states that actually decide the election, shows Obama besting Sen. John McCain by 52 percent to 43 percent among likely voters. The poll has a margin of error of plus or minus three points. (Full data.)

Economic concerns are not only boosting Obama — voters’ views of his economic leadership have improved during the past few weeks:

Independents, key swing voters, now break for Obama, 53 percent to 39 percent, reversing a small lead for McCain after the Republican convention. McCain is the choice of 86 percent of Republicans, while about as many Democrats, 88 percent, back Obama. In the new poll, voters once again gave Obama higher marks than McCain when it comes to dealing with the economy, 53 percent to 39 percent. Two weeks ago, Obama’s edge on the question was a narrow five points, his lowest of the campaign. Among independents, Obama’s advantage on the economy — now 21 points — is greater than at any point in the campaign.

National polls still offer only a rough snapshot of the electorate. Yet this one is striking because it suggests a sharp and unusual turn in the national mood — a kind that never occurred during the last presidential election.

Then, both candidates were locked in such a tight race that neither broke 50 percent in any Post/ABC poll prior to Election Day. Now, as the country faces a major economic crisis and voters look toward the first presidential debate, Obama appears to have consolidated majority support heading into the most crucial phase of the campaign.

In addition, voters are now indicating that they think the race is more important: a record-high 91 percent say they are following it closely, up from 73 percent in July.

This entire lead is within the margin of error, so by the poll’s own (flimsy) standard, the candidates are statistically tied.

Don’t expect that basic fact to ruin a breathless headline, though. Even when they do reflect statistically significant gaps, national polls are often misleading, because they trump up shifts in the electorate that have little impact on the election. A huge spike in Obama’s support in California, for example, does nothing for him in November.

There is, however, one potentially significant trend in this new poll. After all the delegation breakfasts and convention speeches ended, it appears that McCain shored up his party base more than Obama. That’s not surprising. McCain defined his convention by letting the base override his own preferences for a running mate. Ditching Gov. Ridge for Gov. Palin unleashed a multi-day abortion-bashing, media-sniping puritan political orgy. Let There Be Palin, he said, and The Base said it was good.

Since then, McCain’s support among Republicans jumped 8 points, according to the CBS/NYT poll. In the same period, Obama only gained four points among Democrats.

So while both nominees held exactly 79 percent support among their respective parties before the conventions, McCain has now consolidated his base a bit more.

All the national poll caveats still apply, but this has more electoral impact because battleground states with a Republican edge are more likely to firm up for McCain. See Florida, for example, which is now slipping away even though Obama is spending more there, and despite his campaign’s attempt to woo older voters there with trips by both Clintons.

The larger race is still clearly trending Obama’s way. The economy hurts McCain in Ohio, while mortgages hurt him in the Southwest swing states that he must hold for victory, especially Nevada, which led the country in foreclosures this fall. So while the “fundamentals” of his base constituency are strong, the rest of the electorate is still eyeing change.

Update: Commenter “Total” writes: “That’s not what margin of error means. First off, Obama’s up 5 and the margin of error is 3, so it’s not within the margin of error.” Wrong. The margin of error is plus or minus 3, for a spread of six. Thus The Times reports that Obama’s apparent lead is “a difference within the poll’s margin of sampling error.” Total also recommends an analysis by Kevin Drum that stresses how these figures essentially turn on probability, so the “bigger the lead, the more likely that someone is ahead” — even if they are technically within the margin of error. We agree on that one.