DES MOINES — Former Iowa Rep. Jim Leach, a leading Republican moderate, is taking his endorsement of Barack Obama a step further by giving an opening-night speech at the Democratic convention.

Leach, who represented eastern Iowa for three decades, broke ranks with the GOP and endorsed the Democrats’ presidential nominee-to-be earlier this month. Leach is scheduled to speak at the convention in Denver on Monday night.

Brad Anderson, a spokesman for Obama’s Iowa campaign, said Leach’s endorsement shows that Obama’s message of change “appeals to Democrats, Republicans and independents alike.”

“Our campaign is proud to have former Republican Congressman Jim Leach, who is widely respected for his intellect and independent streak, speak directly to millions of Americans on Monday night about how Sen. Obama can bring people together to change Washington,” Anderson said.

When Leach announced his endorsement of Obama earlier this month, he predicted that many Republicans and independents would be attracted by the Illinois senator’s campaign. But, he admitted that his decision to endorse a Democratic presidential candidate wasn’t easy.

“Part of it is political parties are a distant analog to families and you really hate to step outside a family environment,” Leach said when he announced the endorsement.

The 65-year-old was elected to Congress in 1976 and served 30 years before losing his re-election bid in 2006 to Democrat Dave Loebsack. As a moderate, Leach was often at odds with the conservative GOP leadership.

Tucker Bounds, a spokesman for John McCain’s campaign, said Leach is backing a failing agenda.

“Barack Obama opposes additional off shore oil drilling to help Americans end a dependence on foreign oil, still refuses to acknowledge the success of the troop surge responsible for recent success in Iraq and wants to raise taxes on small business during a struggling economy — if Jim Leach supports that failing agenda, that’s his own prerogative,” Bounds said in a statement.

Drake University political science professor Dennis Goldford said Leach is an “old-school, moderate, mainstream Republican who doesn’t have much of a home in the Republican Party nowadays.” Goldford pointed to a GOP that’s dominated by social and religious conservatives.

“This certainly indicates the distance not so much that Leach has moved, but that the Republican Party has moved from Leach,” he said of the former congressman’s upcoming appearance at the Democratic convention.

Obama is scheduled to speak in Davenport on Monday at a town hall meeting. Leach is not expected to attend that event.