KANSAS CITY – Barack Obama renewed his emphasis on economic themes Tuesday, pledging to enforce occupational health and safety regulations as president and declaring that Republican rival John McCain “doesn't get it” when it comes to the anxieties that many middle-class workers are facing.

The Illinois senator was wending his way westward through a handful of battleground states before arriving in Denver to accept his party's presidential nomination at the Democratic National Convention. In Missouri, Obama spoke to workers at a giant hangar where American Airlines planes are serviced. The plant employed 3,500 people in 2001, but the work force has since been cut to about 1,000.

Obama criticized what he called the Bush administration's lax enforcement of OSHA rules, and pledged to strengthen them.

“In a facility like this, the possibility for injury is enormous,” Obama said. He said that in many places, “it's pretty standard to lose an eye, lose a limb, lose a life ... we're going to have a government that makes sure workers aren't put at unnecessary risk.”

Obama has kept a relatively light public schedule this week, not wishing to distract from the carefully scripted program unfolding in Denver. He briefly mentioned the convention festivities Tuesday, praising his wife, Michelle, who delivered a well-received prime-time speech Monday evening.

“What did you all think of my wife?” Obama said to applause. “She was good. I could not have been more proud of her. And she also looked cute, which didn't hurt.”

Aides say Obama's main priority has been preparing the speech he will deliver Thursday night at the giant Invesco Field, home of the Denver Broncos football team.

The stakes are high for his address: He is the first black candidate to win a major party's nomination, accepting the nomination on the 45th anniversary of Rev. Martin Luther King's “I Have a Dream” speech. And it was his soaring address at the 2004 Democratic convention in Boston that catapulted the formerly unknown Senate candidate to national prominence. The speech also offered Obama the best platform yet to persuade skeptical voters that he understands middle class concerns.

Obama has intentionally downplayed expectations for his performance. But his actions have belied his words.

Obama has worked late into the evening several days in a row on the speech, editing the final draft while polishing its delivery. He's consulted on the draft with senior strategist David Axelrod and speechwriter Jon Favreau but has done most of the preparation himself.