CAPE CANAVERAL, Fla. — During his trip to the Kennedy Space Center this week, President Obama will be confronted with an awkward political reality: when it comes to space exploration, sometimes even Republicans can be passionate advocates for the public option.

They’ve joined with Democratic colleagues in Congress to oppose Mr. Obama’s plan to reduce NASA’s missions and to encourage private companies’ rockets to haul cargo and astronauts into space. Mr. Obama’s critics accuse him of abandoning NASA’s glorious trailblazing tradition — and maybe, if your constituents have jobs at NASA, it’s possible to see something pioneering about an agency whose flagship goes a few hundred miles into space.

But four decades after the moon landing, why isn’t NASA venturing somewhere more exotic? The glory days of the Apollo moon missions were possible only because of the race against the Soviet Union, and Mr. Obama could revive that spirit by starting a new space race. But not if he gives in to demands to keep NASA wobbling along in current fashion.

The main problem with NASA is not lack of money. Its current budget is about the same size, when adjusted for inflation, as the average during the 1960s and early 1970s. But space exploration has become so costly that this level of financing won’t even pay for a return to the Moon anytime soon, which is what prompted the White House to cancel the Bush administration’s lunar mission.