Let the general election campaign begin.

Barack Obama, having secured the Democratic nomination Tuesday night, must now pivot to wage a full-time battle against John McCain after spending five months in a protracted and bruising battle against Hillary Clinton.

Obama and McCain, the presumptive Republican presidential nominee, both previewed the tone and message of the race to come during their respective rallies Tuesday, sketching unflattering caricatures of each other that will surely develop in the months ahead.

McCain described Obama as a tax-and-spend liberal, who views government as the antidote to every social ailment and who would be irresponsible in his handling of the Iraq war.

"I have a few years on my opponent, so I am surprised that a young man has bought in to so many failed ideas. Like others before him, he seems to think government is the answer to every problem; that government should take our resources and make our decisions for us," McCain said.

"For all his fine words and all his promise, he has never taken the hard but right course of risking his own interests for yours; of standing against the partisan rancor on his side to stand up for our country. He is an impressive man, who makes a great first impression. But he hasn't been willing to make the tough calls; to challenge his party; to risk criticism from his supporters to bring real change to Washington. I have," McCain added.

In his victory speech after winning the nomination following the final Montana and South Dakota Democratic primaries, Obama offered a preview of characterizations to come about McCain. He accused the Arizona senator of trading in his independent streak to align himself with President Bush's "failed" economic and foreign policies. He suggested McCain is so hung up on the Iraq war that he has overlooked the economic concerns of Americans on the domestic front.

"I honor, we honor the service of John McCain, and I respect his many accomplishments, even if he chooses to deny mine. My differences with him -- my differences with him are not personal. They are with the policies he has proposed in this campaign, because while John McCain can legitimately tout moments of independence from his party in the past, such independence has not been the hallmark of his presidential campaign," he said.

"So I'll say this: There are many words to describe John McCain's attempt to pass off his embrace of George Bush's policies as bipartisan and new, but 'change' is not one of them," Obama continued.

McCain also made a direct invitation to the 18 million-some Democrats who supported Clinton, seen as a more moderate candidate than Obama, especially on national security issues.

Whether or not McCain's efforts will work remains to be seen. Clinton communications director Howard Wolfson, speaking with "Fox & Friends" Wednesday morning, said the intraparty division between Obama and Clinton supporters is worthy noting. But he said he believed the Democrats will mend their fences between now and November.

"There are some people who are disappointed today with what they see. But the differences between Senator Clinton and Senator Obama are very small compared to the differences between either of them and John McCain," Wolfson said.

While leaving open the question of when, how, or if, Clinton would relinquish her quest for the nomination, Wolfson said, "We need to elect a Democrat. We cannot allow four more years of a Bush presidency, which is what we would get in John McCain."

"So Senator Clinton will say to her supporters, as she has said to them already many times," Wolfson sad, "You need to go out and vote for Barack Obama if Barack Obama is our nominee."

While Obama and McCain have both pledged to keep the attacks pegged to policy and not personal, Obama and McCain have 22 weeks until the November general election and plenty of time to cast aspersions in a year that is the Democratic nominee's to lose.

Republicans acknowledge that the political environment poses a threat to their nominee, given the unpopularity of the Iraq war and President Bush's low approval ratings.

But so far, polls show the race is a virtual tie.

According to an average of head-to-head national surveys by RealClearPolitics, Obama is leading McCain by just 1.4 percentage points.

The presidency is decided state-by-state in the Electoral College and so both sides expect a tight race to the very end.

Obama begins with a slight edge. McCain leads in 25 states to Obama's 20, but trails in electors. It takes 270 electors to win the White House.

Obama leads the polls by an average of at least 4 percent in states that yield 242 electors. He is strong on the West Coast and in New England. He also leads in three states Bush carried in 2004 -- the swing states of Iowa, New Mexico and Colorado, a red state McCain can ill-afford to lose.

The states where McCain leads yield 233 electors. His territory stretches across the South and into the Midwestern, heartland states and Western mountain states.

The two candidates are virtually tied in five states, according to an average of the most recent polls compiled by former Bush strategist and FOX News contributor Karl Rove.

They include two of the nation's hardest-hit state economies -- Michigan and Ohio. McCain will need to convince voters he has a solid economic and domestic policy in the face of millions of dollars in attack ads from Obama and Democratic claims that McCain offers nothing but four more years of failed Bush policies.

Both campaigns plan to take about a month to hone their offensive and defensive strategies.

"After they spend a few weeks shooting a lot of different bullets, they're going to figure out which of the bullets are effective, and then you are going to see them start to hammer it home," said Chip Saltsman, who ran Mike Huckabee's unsuccessful campaign for the GOP nomination.

The perceived weak point is different for Obama. He will need to persuade general election voters he is not too inexperienced on national security, while McCain and the GOP hammer him for bad judgment and a short-voting record that is already rated as the most liberal in the U.S. Senate.

He also has some fence-building to pursue with key constituencies, according to Democratic pollster Mark Mellman.

"One is he needs to deepen his relationship with those white working-class voters," he said. "Second, he's got to develop a relationship, a stronger relationship with the Latino community."

McCain, 71, may also face questions and concerns about his age and health, while Obama -- the nation's first black presumptive presidential nominee -- may have to deal with racial undercurrents in the general election campaign as well as linkages to radical left activists.

FOX News' Carl Cameron contributed to this report.