Major Garrett with some sharp analysis on the remaining 3 weeks of the race:

From now until the third and final presidential debate, and quite probably even after that, President Obama and Mitt Romney will fight on the ground, over the airwaves, and in social media over the four Ls and four swing states.

Each of the Ls is a symbol of a larger issue. They are, in no particular order: Libya, Ledbetter, Lying, and Lame. The four swing states are Ohio, Iowa, New Hampshire, and Nevada (more on them in minute).

[...]

Obama advisers contend that the president's criticism of Romney's record at Hofstra stopped his momentum cold and that the economy will remain a threat to Obama. But they added that Romney's own weaknesses--contestable job-creation numbers linked to his 5-point jobs plan, lack of specifics on tax policy, and checkered jobs record in Massachusetts--will keep Obama narrowly ahead. "Romney just makes things up, and over time he's just not believable," said Los Angeles Mayor Antonio Villaraigosa. "I mean, I've never seen anything like it, and people won't stick with someone like that."

What also became clear after the dust began to settle from the rumble on Long Island was the electoral map has narrowed and Obama's team, while conceding nothing publicly, is circling the wagons around Ohio, Iowa, New Hampshire, and Nevada. Plouffe said that Obama remains strong in all four states, but he would not discuss the specifics of internal polling or voter-contact analytics, saying only that Obama has "significant leads" in all four places.

It is uncharacteristic of Team Obama to concede any terrain, but Plouffe offered no such assurances about Obama's position in North Carolina, Virginia, or Florida. Romney advisers have seen big gains in all three states and now consider wins likely, although not guaranteed, in all three. They are similarly upbeat about prospects in Colorado but not confident enough to predict victory. That Plouffe left Colorado off his list of states where Obama's leading and can withstand a Romney surge might be telling.

From here on out, you can get a sense of the race by watching where the candidates (and their running mates) are traveling. Ohio will get the saturation treatment from both Obama and Romney, but if Obama or Biden makes only rare trips to FL and VA (NC is pretty much out of reach for Obama already according to many observers), you know that he is virtually conceding those states to Romney. Similarly, if Romney avoids Iowa and New Hampshire, you would be correct in thinking he doesn't see much chance for the ticket in those states.

Another tell tale sign is where the campaigns are spending money on advertising.This is the time when campaigns who have husbanded their resources let everything go in a rush. A big ad buy by Romney:

The ad buy - timed to start the day after the second presidential debate - will cover both cable and broadcast television in nine states: Colorado, Florida, Iowa, Nevada, New Hampshire, North Carolina, Ohio, Virginia and Wisconsin.

The biggest amounts will be spent in Ohio (about $2 million), Virginia ($1.5 million) and Florida (more than $3 million).

Read Garrett's electoral scenarios for some excellent background on how the last 3 weeks might play out.