WASHINGTON – Republican presidential candidate Mitt Romney raised questions about US President Barack Obama’s approach to foreign leaders Wednesday after he won three primaries and moved closer to clinching the GOP nomination.Speaking to the Newspaper Association of America the day after he prevailed in the Wisconsin, Maryland and District of Columbia votes, Romney attacked Obama for having been caught on a live microphone last week telling Russian President Dmitry Medvedev that he would have “more flexibility” to deal with controversial issues like missile defense after the November election.Calling the comment “deeply troubling,” Romney charged that “that incident calls his candor into serious question.”“What exactly does President Obama intend to do differently once he is no longer accountable to the voters?” Romney asked.“Why does ‘flexibility’ with foreign leaders require less accountability to the American people?” “President Obama has made clear his intentions on missile defense both in word and deed,” a source close to the Obama campaign hit back. “This administration has a strong national security record that illustrates an understanding of today’s military and security threats.”The source continued, “The real question is what kind of commander-in-chief Mitt Romney would be when he still believes Russia is our number one foe, showing a real lack of understanding of what the world looks like today.”Following Obama’s exchange with Medvedev last week, Romney had criticized Obama for the assurances he had offered “our number one geopolitical foe.” Obama personally increased the heat on Romney Tuesday, for the first time attacking the GOP challenger directly by name.Obama’s lambasting of Romney for his backing of the Republican draft budget was a sign that the president sees the former Massachusetts governor as his key competitor and the GOP primaries as heading toward the finish line.However, Romney’s main opponent, Rick Santorum, has vowed to stay in the race and spent Wednesday appealing to voters in his home state of Pennsylvania, where he once served as senator. Pennsylvania holds its presidential primary on April 24.But Romney’s triple win on Tuesday helped him consolidate his lead and gave him an overwhelming advantage in delegates.Romney now has 652 to Santorum’s 269. Former speaker of the US House Newt Gingrich is next with 140 and Texas Representative Ron Paul is last with 67.Additionally, Romney prevailed in most cases among groups that have been seen as his weakest constituencies: Evangelicals, strong conservatives and Tea Party supporters.According to exit polls, Romney swept all three constituencies in Maryland, and took strong conservatives and Tea Party supporters in Wisconsin as well. He did lose among Wisconsin evangelicals to Rick Santorum, but only by 4 percent.Romney’s focus during his Tuesday night victory speech and Wednesday address was squarely on Obama and the general election in November.