I've seen it put that a big problem with the US space program is that every President comes in with a different vision of what it should be, and so the wheel keeps being reinvented. In Russia, they've just kept using the same design since they started.
That's quite true. The American Apollo program was cut short by a combination of the expenses of the Vietnam War, and (reportedly) Richard Nixon's desire to stamp out something associated with JFK (who of course beat his ass in the 1960 election). Werner Von Braun's ambitious Apollo Applications Program was chopped down to Skylab, and the United States didn't make a single manned space flight from mid 1975 through April 1981 because NASA was developing Nixon's darling, the Space Shuttle. Hell, two complete Saturn 5s and two complete Saturn 1Bs went completely unflown (you can see components of them at Cape Canaveral, Houston, and Huntsville)
During the Duhbya Administration, Project Constellation was announced to be the post-Space Shuttle manned space flight program. In 2010 the Obama Administration cancelled Constellation, and announced the Space Launch System.
The Russians, meanwhile, have been using essentially the same Vostok launch vehicle since 1961 (modified and modernized over time, but essentially the same). The Soyuz spacecraft that ferry cosmonauts and astronauts to the ISS has gone through three design upgrades, but is essentially the same spacecraft that first flew in 1967, about the same time Apollo was getting ready for its first mission.
So, yeah, NASA's been a poliitical football for a long time. If Obama's successor is a Republican, the SLS will undoubtedly be cancelled and replaced with something else. If Obama's successor is a Democrat, well, it might
still be cancelled and replaced with something else.