On one topic -- Iran -- Romney has found some traction. He has sharply criticized Obama on Iran policy, an area where the president is clearly vulnerable. Americans disapproved of Obama's handling of Iran's nuclear potential by a 52 to 36 percent margin in a March Washington Post-ABC News poll, with twice as many strong detractors as supporters.
But it's not clear whether Romney is landing clean punches. In February, 49 percent of voters in a Fox News poll were at least "somewhat confident" that Obama could stop Iran from getting nuclear weapons; 44 percent said the same of Romney. And Romney's more confrontational approach may not ring as true to voters in the general election as it did in the Republican primary. Most Americans in a Washington Post-ABC News poll last month preferred diplomacy over pre-emptive military action.
Afghanistan may be an even rockier issue, as public support for continuing the mission is on the wane. Obama plans to withdraw troops in 2014, but support for the war effort overall has fallen since last year, with fewer Americans seeing the effort as worth the costs.
More than half of the public -- 54 percent -- say the United States should withdraw military forces even if the Afghan army is not adequately trained, according to a March Washington Post-ABC News poll. In a recent CNN/ORC poll, 55 percent said the U.S. should remove all troops before 2014, while just 22 percent wanted them to stay beyond that year.
Romney has yet to capitalize on these weaknesses, and his upcoming speech may represent a major attempt to do so. But he may need to go beyond merely criticizing Obama to convince voters that he'll be a steadier hand on the international stage.