WASHINGTON — John McCain said this week that he would exclude NASA from his across-the-board freeze on government spending that he has proposed — the first time that the Republican presidential nominee has singled out the space agency to be spared. The statement could put to rest longstanding — and conflicting — stances by the Arizona senator, who has called for both the freeze and increased support for NASA, which gets roughly $17 billion annually in the federal budget. He has promised to boost NASA funding by $2 billion. “I will freeze government spending on all but the most important programs like defense, veterans care, NASA, Social Security and health care until we scrub every single government program and get rid of the ones that aren’t working for the American people,” McCain said Wednesday in Miami. Space policy could be a tipping factor in Florida, where thousands of workers at Kennedy Space Center are likely to lose their jobs once the space shuttle is retired, now planned for 2010. The $2 billion increase in funding proposed by McCain — and echoed by Democratic nominee Barack Obama — is targeted at closing the flight gap between the shuttle’s retirement and the first mission of its successor, now under development and slated for a first mission in 2015.