EUGENE, Ore. (AP) _ Attempting to lay a symbolic claim to his party's presidential nomination, Democrat Barack Obama will mark the latest round of primary voting with a rally in Iowa, where his solid win in January caucuses propelled him to his status as the front-runner.

Obama was campaigning Saturday for primaries Tuesday in Oregon and Kentucky as his aides announced the rally on primary night in Iowa, which they described as "a critical general election state that Democrats must win in November."

Rival Hillary Rodham Clinton has a strong lead in polls in Kentucky, but Obama has the advantage in Oregon.

Obama has built a solid lead in Democratic National Convention delegates over Clinton, and is working overtime to cast an image of inevitability to his campaign for the nomination. In recent days, he has spent more time focused on his differences with certain Republican nominee John McCain than sparring with Clinton.

While touring a hospital Saturday, Obama was asked by X-ray technician Ron Spooner, "How do I know that I can trust you?"

"The nice thing is we're going to have four more months, five more months of active campaigning where you can watch and see if I am consistent, do I stay honest," said Obama. "Let me take your advice and let me make sure that I try to stay honest in what is sometimes a dishonest profession."

Though health care was his theme of the day, Obama returned to a debate launched Friday with McCain on foreign policy. Both President Bush and McCain suggested that Democrats couldn't be trusted to be tough on terrorists, a charge Obama has rejected.

"The other side is going to keep calling us the same names, making the same cheap shots, using the same fear tactics they've used for the last four decades," said Obama.

Obama spoke to about 1,400 at a town hall meeting in Roseburg, arguing that McCain would merely follow a failed policy set by Bush.

"If you agree that we've had a great foreign policy over the last eight years, then you should vote for John McCain, you shouldn't vote for me," said Obama. "That's what this debate is all about, that's the choice in this election. Do you want more of the same or do you want change?"

McCain spokesman Tucker Bounds argued that Obama's foreign policy shows "incredibly weak judgment. We're a nation rooted in a history of sacrifice and achievement, not in lofty campaign rhetoric or campaign promises."

Iowa has been a swing state in recent presidential elections. Democrat Al Gore narrowly carried the state in 2000, and President Bush collected the state's seven electoral votes by just over 10,000 votes in 2004. Since that time, however, Democrats have built a substantial edge in registered voters, and turnout in the January precinct caucuses was at record levels.

Obama will be joined by his wife, Michelle, for the Iowa rally, a homecoming of sorts for the couple. The rally is the latest effort by Obama to shift attention away from the primary season to the November election even though Clinton continues to maintain a full campaign schedule in primary states.

Touring an outdoor fair in Keizer, Obama said the swing would be a nostalgic one.

"It'll be a nice reunion with everybody who helped us get started," said Obama.