(CNN) -- Sen. Barack Obama took his campaign to Miami, Florida, on Saturday with a message to the nation's mayors: I'll be your ally in Washington; Sen. John McCain will not.
Speaking to the U.S. Conference of Mayors, the presumptive Democratic presidential nominee praised McCain's service to the country but chastised him for not "proposing a strategy for American cities" hit hard by tough economic times.
"Because while Sen. McCain is a true patriot ... he won't be that partner. His priorities are very different from yours and mine. ... He isn't proposing a strategy for America's cities. Instead, he's calling for nearly $2 trillion in tax breaks for big corporations and the wealthiest Americans."
Obama also hit hard on McCain's trip to Iowa this week to see firsthand the effects of devastating flooding.
"Both Sen. McCain and I have traveled recently to the areas that have been devastated by floods. And I know that Sen. McCain felt as strongly as I did feeling enormous sympathy for the victims of the recent flooding. ... And I'm sure they appreciated the sentiment, but they probably would have appreciated it even more if Sen. McCain hadn't opposed legislation to fund levees and flood control programs, which he considers pork."
Shortly after Obama's speech, the McCain campaign lashed out, saying the Illinois senator opposed and even voted against a bipartisan effort in the Senate by McCain; Sens. Russ Feingold, D-Wisconsin; and Claire McCaskill, D-Missouri; to ensure that levees were fixed first.
"It is beyond the pale that Barack Obama would attack John McCain for actually trying to fix the problem and change the way Washington works. Barack Obama's willingness to continue the status quo pork-barrel politics in Washington, and then engage in political attacks that entirely disregard the facts, once again fundamentally shows that he's nothing more than a typical politician," McCain spokesman Tucker Bounds said.
At issue is the 2007 Water Resources Development Act, a $23 billion bill that funded levee and flood control programs along with dozens of other projects across the country, including Everglades and other habitat restoration, emergency water supply storage, lock and dam security, and water quality improvement.
The bill passed Congress, with Obama in favor and McCain opposed, although neither took part in the final vote.
The measure was vetoed by President Bush as too expensive, but that veto was overridden, a first for the president. Neither McCain nor Obama participated in the override vote.
The Senate votes were 91-4 for the first vote and 79-14 for the override.
During the initial debate in the Senate, Obama voted against an amendment, sponsored by Feingold and co-sponsored by McCain and others, that would have established a commission to prioritize water projects, with flood control at the top of the list.
Thirty-five Republicans joined 34 Democrats in rejecting the amendment. Although he was a co-sponsor, McCain did not vote on the amendment. McCaskill, who was not a co-sponsor, voted in favor of it.
Meanwhile, Obama praised several mayors, including New York's Michael Bloomberg's efforts to find new ways to improve his city's economic and crime rates.
Bloomberg, who called on the Jewish community in Florida this week to avoid rumors about Obama, has yet to endorse either candidate.
Obama also took time to thank mayors for their help on the "front lines in our communities."
"You may get more than your fair share of the blame sometimes. You may not always be appreciated. But when a disaster strikes -- a Katrina ... or a six-alarm blaze -- it's city hall we lean on, it's city hall we call first and city hall we depend on to get us through tough times. "
On Saturday, he also proposed a policy initiative aimed spurring economic growth in communities.
The Innovation Clusters program will provide planning and matching grants for regional business, government and university leaders to "collaborate on leveraging a region's existing assets -- from transportation infrastructure to universities -- to enhance long-term regional growth," according to his campaign.
"There's no better place to start than by investing in the clusters of growth and innovation that are springing up across this country. ... When we take the different assets that are scattered throughout our communities ... and bring them all together so they can learn from one another and share ideas, you get the kind of creative thinking that doesn't come in isolation."
He said that plan will lead to "more innovation and entrepreneurship and real economic benefits like new jobs and higher wages," citing Pennsylvania's Keystone Innovation Zones, which he says have led to the formation of nearly 200 new companies.
Obama said that if he is elected, his administration will offer $200 million a year in competitive matching grants for state and local governments for regional economic growth.
Meanwhile, Obama heads west next week to campaign in two states he hopes he can turn blue this November. He is scheduled to hold campaign events in Albuquerque, New Mexico, on Monday and Las Vegas, Nevada, on Tuesday.
CNN considers Nevada a battleground state, one that both parties think they can win in the general election. President Bush carried Nevada in 2004, but by only 2 points over John Kerry.
CNN also considers New Mexico a state that leans Republican, but the Obama campaign has the state in its sights.
President Bush won New Mexico as well four years ago, but by only 1 percent, and New Mexico Gov. Bill Richardson is a major Obama supporter.
Geography also comes into play here. Arizona borders both states, and that is McCain's home state. Interactive: CNN's electoral vote map »
The presumptive GOP presidential nominee will also go west next week. He starts his week with fundraisers and campaign events in California.
CNN's Ed Hornick, Steve Brusk, Tasha Diakides, Alexander Marquardt, Rebecca Sinderbrand, Paul Steinhauser and Chris Welch contributed to this report.