McCain in battleground states as Democrats fight on

(CNN) -- Sen. John McCain is looking to make the most of a golden opportunity this week in a string of battleground states, while the fight drags on for the Democratic presidential nomination.

The presumptive Republican presidential nominee is campaigning Friday in Denver, Colorado. In other stops this week, he unveiled a health care proposal in Florida, toured a cancer research center in Cleveland, Ohio, and attended a town hall-style meeting in Iowa.

While in Ohio, McCain tried to address blue-collar concerns that foreign trade and globalization have led to lost jobs at home.

"We have failed miserably to give education and training to our workers," McCain said. Watch McCain's pitch to independents »

All four swing states McCain visited could play a pivotal role in the general election, and he is using the spring to appeal to independent and even Democratic voters that wouldn't traditionally back a Republican.

"He's got an opportunity to present himself as a different kind of Republican, which is pretty important in this climate," said GOP pollster Whit Ayres. "He is as popular, if not more popular, among independents than he is among Republicans. Independents are going to decide this election." Watch as McCain calls for a gas-tax holiday »

But McCain has not gone unchallenged while Sens. Hillary Clinton and Barack Obama remain in a bruising fight for the Democratic nomination.

The Democratic National Committee, liberal groups such as MoveOn.org and labor unions all have launched anti-McCain television ads.

MoveOn.org's $1 million advertising campaign picks up remarks from McCain that he "would be fine" with U.S. troops in Iraq for 100 years.

"Now, we need to know how long we'd be in Iraq if John McCain were president," the announcer says in the MoveOn.org spot.

The DNC's $500,000 ad campaign also hits the senator on his Iraq comments.

"If all he offers is more of the same, is John McCain the right choice for America?" the announcer asks in the DNC commercial.

McCain said the ads deliberately take his words out of context, noting that he qualified his statement by saying he would support the long-term deployment of U.S. troops in Iraq if the conditions were relatively peaceful and similar to the deployment of troops in Germany, Japan and South Korea. Watch McCain say he was right on Iraq »

The Service Employees International Union on Thursday bought nearly $1.5 million worth of TV airtime in Ohio criticizing the Republican's health care proposal, according to a report filed with the Federal Election Commission.

"Like President Bush, John McCain won't stop rising health care costs," the announcer in the union ad says, adding that the senator "joined Bush to oppose health care to children." The latter is a reference to the president's veto last year of a bill to expand the State Children's Health Insurance Program.

McCain also is quick to note his disagreements with the Bush administration, including opposition to the "Mission Accomplished" banner on the USS Lincoln as the president marked the end of "major combat operations" in Iraq.

Thursday was the five-year anniversary of Bush's speech.

"I thought it was wrong at the time," McCain said, referring to the banner. "I thought that phrases like 'a few dead enders,' 'last throes,' all of those comments contributed over time to the frustration ... of Americans."

McCain has said he doesn't want to rehash the last five years but turn the debate about the Iraq war into what comes next.

"I said ... more than a year ago I'd much rather lose a political campaign than lose a war, and I still stand by that statement," McCain said.

"My knowledge and experience, which Sen. Obama and Sen. Clinton do not have, dictate to me that we must succeed and the strategy is succeeding with spikes and with enormous difficulty and enormous sacrifice."

But with U.S. deaths in Iraq on the rise again after a period of relative calm, it is impossible to know how voters will look at Iraq on Election Day. E-mail to a friend

CNN's Rebecca Sinderbrand contributed to this report.

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