WASHINGTON -- Mitt Romney told business leaders Wednesday President Barack Obama is largely responsible for the nation’s sluggish economy, but a Romney presidency would mean big changes that would make it easier for them to run their companies.

A day before Obama plans a campaign speech on the economy, the presumptive Republican presidential nominee offered sharp, sometimes stinging, contrasts.

“If you look at his record of the last three-and-a-half years you will conclude, as I have, that it is the most anti-investment, anti-business, anti-jobs series of policies in modern American history,” Romney told about 100 executives at a meeting of the Business Roundtable at Washington’s Newseum.

“He is not responsible for whatever improvement we may be seeing,” Romney said of Obama. “Instead, he is responsible for the fact that it’s taken so long to see this recovery and the recovery is so tepid.”

Get ready, Romney said, for a “watershed election which will determine the relationship between citizen and enterprise and government.”

Obama will talk about his vision in Cleveland on Thursday, hoping to boost a campaign that’s run into trouble recently. While the two men are close in head-to-head matchups, polls suggest warning signs for Obama on the economy, particularly since a poor jobs report for May sent the unemployment rate back up and suggested a disturbing trend, if sustained, for an incumbent five months before Election Day.

In battleground Pennsylvania, for example, a recent poll found that Obama has the lead overall, but that voters there prefer Romney on the economy, the dominant issue. Nationally, Romney now has an edge among middle-income voters, according to a Gallup Poll.

Romney listed some changes he’d try to implement quickly – changes that could be difficult if Democrats win control of one or both chambers of Congress.

The National Labor Relations Board, Romney said, would be “restructured,” with those friendly to labor replaced. The size of government would be cut. “I’m going to go after government,” he said. More domestic oil exploration would be encouraged. Taxes would be lower. Romney wants to cut marginal income tax rates by 20 percent. He has not specifically addressed how he’d make up the revenue.

He discounted Obama’s scheduled campaign speech on Thursday as more of the same. “My own view is that he will speak eloquently, but that words are cheap and that the record of an individual is the basis upon which you determine whether they should continue to hold onto their job.”

The Republican found a sympathetic, if somber, audience Wednesday, offering them an indictment of Obama’s economic record and then his own remedies.

“He said as you know, just a few days ago, that the private sector is doing fine,” Romney said. “But the incredulity that came screaming back from the American people has caused him, I think, to rethink that.”

The 2010 federal health care law, for instance, “demonstrated a lack of understanding what American people are experiencing,” Romney contended. He said Obama’s energy policies are designed to push up prices of traditional energy sources so that people will rely more on alternatives such as wind and solar.

“The government has to be the partner, the friend, the ally, the supporter of enterprise, not the enemy,” Romney said.

The Obama camp Wednesday countered that a Romney presidency would be a return to the freewheeling business environment that in 2007 helped trigger the nation’s worst downturn since the 1930s.

Romney would push “budget-busting tax cuts for the wealthiest Americans and letting Wall Street write its own rules – the same policies that crashed the economy and devastated the middle class in the first place,” said Obama campaign spokeswoman Lis Smith.

“Mitt Romney made dishonest after dishonest claim about the president’s record and failed to offer any new ideas of his own on how to improve the economy and strengthen the middle class,” Smith said.