The first problem W would face as self-declared fuhrer would be regional loyalty. He could quickly find himself dictator of the red-state south, the rest of the country effectively being self-governed at the state level. Keep in mind that W's approval ratings are at historic lows. Whatever comity he can expect from the lobbyist-owned congress and hack-judiciary will not necessarily be matched by the people. After a coup, in the face of massive popular outrage, who is to say the governors of Washington, or California, or Massachusetts, or Minnesota will take orders from DC?
That is where the national military comes in, of course. Notice that all the leading Democrat presidential candidates are all lined up lock-step behind the idea that our military needs to be larger by 100,000 troops. America faces no credible military threats from anywhere. Our historic commitments to defend South Korea and western Europe from land invasion are looking a little stale. The only reason we need more troops is:
1) To occupy more of the Middle East and fight all the Israeli proxy wars that AIPAC has in mind. We can't hold Iraq and invade Iran with the current force.
2) To keep the beltway crowd in control of the country if they decide to suspend the constitution and enter "continuity."
NSPD-51 and annexes come formally from the Bush White House, but essentially all the beltway players are on board (as with warrantless surveilance and every other partial erasure of the constitution already accomplished), along with the corporate media. Hence what Rosenbaum as observed: not a peep from Congress, the media, or the think tank crowd. An extra 100,000 troops would enable the beltway to wage Israel's wars indefinitely and still enforce martial law at home if necessary.
These are the same troops who can pull a Haditha and later say with a straight face they did nothing wrong. If martial law comes down on America, it will be like Argentina in the 1970s, and alas too late to state the obvious -- we made a mistake putting these people in power.
It's a paradox, and incorrect to say, but true: our armed forces don't fight for our freedom any more. They imperil it. What we desperately need is 100,000 fewer troops. Then you could be sure the beltway crowd won't bother with a coup.