Hillary Rodham Clinton tried to boost her presidential campaign in the leadoff voting state of Iowa on Monday by embarking on a Fourth of July tour accompanied by one of the most popular figures in Democratic politics — her husband.

Bill Clinton said he is backing his wife because she is the most qualified, not because of any spousal obligation.

"All you have to do is decide who do you think will be the best president," he told thousands of voters gathered at twilight on the Iowa State Fairgrounds. "Here's what I want to say to you: I'd be here tonight if she asked me if we weren't married."

His wife, a New York senator, said she was "thrilled to finally find something in politics that I'm doing that my husband didn't do." Bill Clinton skipped the Iowa caucuses in 1992 because Iowa Sen. Tom Harkin was running against him.

Normally a spouse's presence on the campaign trail isn't so noteworthy, but so far the Clinton campaign has been using Bill Clinton only sparingly. Monday's rally was the first time they had campaigned together in an early voting state, and he planned to stay at her side through the July 4 holiday.

The former president's visit comes six weeks after an internal campaign memo by a senior staffer suggested she should skip Iowa and invest her resources in other early voting states. Clinton denounced the memo, which called Iowa "our consistently weakest state," and said she would continue to compete vigorously in Iowa.

Clinton leads the Democratic field in most polls, but she has yet to break out from rival John Edwards in Iowa, which is scheduled to hold the nation's first presidential caucus on Jan. 14.

After the Clintons' trip was announced, Democratic rival Barack Obama said he would be visiting the state with his wife and daughters in a dueling family holiday.

Obama was to begin Tuesday, while the Clintons began Monday night with a rally made for Iowa television, surrounded by hay bails stuck with little American flags and thousands of flag-waving supporters.

Bringing out Bill Clinton is not without risks. He tried not to overshadow his wife at the fairgrounds, keeping his remarks to an uncharacteristically brief 8 1/2 minutes. Republicans used the joint appearance to remind voters of their personal problems.

"After Bill Clinton tarnished the name of the president of the United States, the Republican Party restored hope, respect and morality within the Oval Office by bringing positive ideas and conservative values back to the White House," the Iowa Republican Party said in an e-mail sent to reporters. "Neither Iowans nor the rest of the country need to witness another Clinton catastrophe."

Bill Clinton is especially beloved by Democrats who will decide the nomination. According to a CBS News poll, 79 percent of Democrats view Bill Clinton favorably, compared to two-thirds who said they have a favorable view of his wife.

Elementary school principal Clark Wicks of Perry, Iowa, said he thinks of Bill Clinton as a strong president who did a lot of good for the country.

"He made a lot of poor choices on the side," Wicks said, sitting with his wife under a shade tree before the event started. "But, boy, not as many as our current president on the economy, the war, education."

Bill Clinton only joined his wife publicly once before since she announced her candidacy — during a commemoration of the civil rights march in Selma, Ala., where Obama, the only black candidate in the race, threatened to overshadow her.

Clinton got another boost from an important spouse among Iowa Democrats — Ruth Harkin, the wife of the senator, announced she would back her and introduced them at the fairgrounds. Ruth Harkin was president of the Overseas Private Investment Corp. in the Clinton administration. Her husband has said he will remain neutral.