Mitt Romney criticized President Obama’s decision to stop deporting some illegal immigrants who were brought to the United States as children as an election-year political move, but he repeatedly declined in an interview Sunday to lay out an alternative plan.

The presumptive Republican presidential nominee said he wants a “long-term solution,” unlike what he derided as Obama’s “stopgap measure,” but would not say what it would entail other than to provide permanent residency to those who serve in the military.

“With regards to these kids who were brought in by their parents through no fault of their own, there needs to be a long-term solution so they know what their status is,” Romney said on CBS’s “Face the Nation.”

Romney’s struggle to offer a clear alternative on the immigration issue was a fresh reminder of one of the challenges he faces, which is to go beyond his steady criticism of the president with a more detailed description of the policies he would implement to replace what Obama has done.

Immigration is a problem particularly because of conservative stances Romney took during the Republican primary campaign that now could cause him difficulty in appealing to Hispanic voters in the general election. But even regarding the biggest issue of the campaign — the economy — there are many unanswered questions as to what he would do.

Romney is midway through a bus tour of six potential battleground states and on Sunday, he stumped across the most critical of all, Ohio. He spoke at a pancake breakfast in Brunswick and a rally in the town square of Newark and then campaigned with House Speaker John A. Boehner (R-Ohio) at a hamburger shop in Troy.

But his speeches were short and general. At the rally here in Newark, Romney revved up a couple of thousand supporters by promising to “shock the world with how our economy’s coming back,” but in a speech that clocked at just nine minutes, offered only broad outlines and few specifics.

Those specifics included developing U.S. energy resources, cutting back on government regulation of business — including the repeal of Obama’s health-care law — and putting the country on track toward a balanced budget.

Stuart Stevens, the campaign’s chief strategist, acknowledged that voters want to know more about what a Romney presidency would be like. But he took issue with critics who have said the Republican hasn’t offered details about how his presidency would differ from Obama’s.

“As the campaign goes on, you’ll have more specifics,” Stevens told reporters Sunday after the Newark rally. “But I think that Governor Romney has been more specific [than] the president on most of these big issues.” He cited Romney’s proposals on Social Security and Medicare as two examples. But he begged off questions about immigration and how Romney would balance the budget.

Stevens said voters have a clear sense of Obama. “They know how they feel about this president,” he said. “They know what they’ve experienced the last 31 / 2 years and they’re disappointed.”

But he acknowledged that many of these same voters don’t know Romney well. “We hear the same thing,” he said.

The campaign’s response has been an opening round of ads, which describe, in general terms, what the candidate would do in the opening stages of his presidency. “Okay, let’s talk about what a Romney presidency would be like,” Stevens said, adding: “People want to know this.”

The renewed spotlight on immigration comes as Romney tries to narrow Obama’s wide lead among Hispanic voters. The candidates will address a national group of Latino officials this week in Orlando, where Romney will face pressure to further define his position.

Romney made his first extensive comments in the CBS interview about immigration policy since Obama’s announcement Friday regarding the citizenship status of child immigrants who go on to become law-abiding residents.

When anchor Bob Schieffer asked Romney whether he would repeal Obama’s policy, he said: “Well, it would be overtaken by events, if you will, by virtue of my putting in place a long-term solution, with legislation which creates law that relates to these individuals such that they know what their setting is going to be, not just for the term of a president but on a permanent basis.”

Romney, a former Massachusetts governor, suggested that Obama’s decision was motivated by politics, not policy.

“If he felt seriously about this he should have taken action when he had a Democrat House and Senate, but he didn’t. He saves these sort of things until 41 / 2 months before the general election,” Romney said. Campaign politics, he added, was “certainly a big part of the equation.”

Sen. Marco Rubio (R-Fla.) has been trying to draft compromise legislation for young immigrants, but Romney largely has been standoffish, declining to take a position on the outlines Rubio has described.

And in his campaign appearances Sunday in Ohio, Romney never mentioned immigration. Instead, he focused almost exclusively on the economy and sharply criticized the president’s stewardship of it.

In a sign that the campaign is intensifying, though, Romney was followed by hecklers at two of his rallies; at an event in Troy, about a dozen Obama supporters shouted, “Romney, go home!” and “We are the 99 percent!” throughout Romney’s eight-minute speech. Earlier Sunday, Obama strategist David Axelrod tweeted: “I strongly condemn heckling along Mitt’s route.”

When Romney’s bus drove in dramatic fashion onto a rolling apple orchard in Brunswick, his breakfast crowd was drenched and the pancakes were soggy. But the candidate — accompanied on Father’s Day by his wife, Ann; two of their five sons; and five grandchildren — pointed to the weather as a political good omen.

“I didn’t know it was going to rain this morning,” Romney said, as the storm clouds began to drift east. “It looks like the sun is coming out. I think that’s a metaphor for the country. The sun is coming out, guys. Three-and-a-half years of dark clouds are about to part.”