By Vaughn Ververs
CBSNews.com senior political editor

“Joe the plumber” achieved sudden national fame in the final presidential debate, but it was John McCain who needed the headlines. Although the Republican nominee was energetic, focused and, at times, emotional in his last on-stage appearance before Election Day, it was likely not enough to change the underlying trajectory of the race.

With Barack Obama by all accounts holding a solid lead and less than three weeks to go, McCain came out aggressive from the very beginning. He grabbed onto a recent exchange Obama had with a small businessman, Joe “the plumber” Wurzelbacher, and used it like a hammer to pound away at the Democrat as a tax-and-spend class warrior. “Hey, Joe, you’re rich, congratulations,” McCain said at one point to illustrate a point about the level of taxation in Obama’s plan.

McCain took what many in his own campaign reportedly thought to be a risk by directly raising the issue of Obama’s association with William Ayers, challenging him to describe the fullness of their relationship. He emotionally described how hurt he was by assertions by Rep. John Lewis about some crowd behavior at McCain’s campaign rallies, then turned around and accused Obama of disparaging his supporters. He jumped in at awkward moments, rolled his eyes and demonstrated near-contempt at Obama’s answers.

And he pointedly sought to distance himself from President Bush, both on issues and seemingly personally. As if taking offense to the continued comparison, McCain curtly told his opponent, “Senator Obama, I am not President Bush. If you wanted to run against President Bush, you should have run four years ago.”

The kitchen sink was not thrown in but one sensed it was positioned under the table and within reach, just in case it was needed.

What McCain did not manage to do was ruffle the ever-calm, cool and collected Obama. As he has been several times during these debates, the Democrat was on the defensive at several points, especially on taxes. Obama continues to refuse to say which of his big-idea proposals he’d have to shelve because of economic realities, instead choosing to focus on those he won’t put aside. If he’s not a big taxer, as McCain asserts, he certainly has a lot of things he wants to spend on.

But Obama continues to do a masterful job talking directly about and to the middle class. Polls show overwhelmingly that voters trust Obama more on the economy than McCain and he used that as a wedge to keep it that way. “What we haven’t yet seen is a rescue package for the middle class,” he said when discussing the Wall Street bailout and John McCain’s mortgage proposal.

The Illinois Senator was clearly prepared for the William Ayers issue and McCain’s attempts to link his campaign to ACORN, the group which has spurred a flood of voter registration controversies. And while he engaged McCain on who’s responsible for the negative tone of the campaign, his heart didn’t seem to be into a prolonged exchange. Obama wanted a quiet, low-key affair and for his part, he pulled it off.

The campaign now moves into its most intense phase, if such a thing is even possible in a campaign that has redefined the concept. With just 20 days to go, there’s no longer any room for error, adjustment or new approaches. Americans have seen these two candidates at three of these debates now and they’ve seen a striking contrast – McCain has been at turns uplifting and irritated, if not flat-out angry, while Obama remains steady and level, almost too cool at times.

Those traits were clearly on display last night in New York. McCain did a better job of explaining his economic philosophy than he has during this entire campaign, and perhaps it’s better late than never. If not the inspirational, transformational leader he was billed as over the past year, Obama has gone a long way toward making voters feel comfortable seeing him as a president.

Even though he was uneven at times, McCain likely did himself some good last night, particularly among voters like “Joe the plumber” who worry about Obama’s plans for country and remain open to the Republican argument. The problem for McCain, less than three weeks from the election, is that there simply might not be enough of those voters left to do him much good.