Despite gains made by the Republican Party, support for activist government remains very strong. Evidence from Gallup shows that Americans tend to be ideological conservatives but operational liberals.
The mystical center is where Obama's disaffected base resides. He doesn't have to choose. Both swing voters and the Democratic base want the President to stand up to Wall Street on behalf of main street.
Even if New START is ratified before the Democrats' Senate majority significantly shrinks, it will not help advance nonproliferation advocates' long-term goals unless a lost consensus on arms control fundamentals is rebuilt first.