I remember when I was in high school, in my American Government class in the back with all the kids who didn't particularly want to be there. I wanted to be there, I thought it was interesting, but you can learn plenty from the back and the other kids don't hate you for being so smart if they think you're angry and antisocial and get bad grades. You don't have to actually get bad grades, just tell people that you do; I learned that when I was six years old.
Anyway, American Government was a decent class, our teacher was really into history and how great America is, and enthusiastic teachers are always better than drones, but I spent most of my time passing notes with this angry pothead guy so it didn't look like I was learning. This was back in 1999 or 2000, if I remember correctly- before 9/11, but after the Oklahoma City bombing and the conviction of Tim McVeigh. As it was a government class, we got to talking about how, theoretically, one would take over the American government, were one so inclined.
The guy I sat next to- I don't even remember his name- started out talking about needing soldiers and secret police and all that, assassinating the president and holding DC hostage with a nuclear weapon, typical doomsday movie scenarios. But I really thought that the best way to begin taking over the United States would be to start a terrorist organization, parallel to a successful political career. You'd have to have a small group of people to help you, of course, and you'd have to have the politician kept strictly separate from any ties to the terrorist group. In fact, you'd want the politician in operation for several years before any sort of terrorist activity was apparent.
So you'd have a politician, male and handsome and with a team of intelligent people of a moderate political bent, and you'd get him elected, perhaps to the Senate. And then once he'd made a name for himself as a uniter, not a divider, you'd want to get him made something like Secretary of Defense, or of State or something along those lines- powerful but not too prominent. Secretary of State would be best, because then he's in line for the Presidency. And then once he's ensconced in power, you start up with the terrorist group, which by this point should be spread across the country and should have a good amount of supplies and connections.
This terrorist network would not be much like al Qaida; it would be domestic, probably extremely religious, composed of white men in crewcuts who believe the time has come to get rid of the federal government via the Second Amendment. These people would be crazy fanatical and would bomb several locations across the country, killing as many people as possible, preferrably, for our purposes, children or the elderly.
This then is where the two elements of the plan tie together: the politician steps up to save the country from the terrorists by exerting control over public meetings, broadcasting, trade, etc. If possible, he gets it declared a state of emergency. If people protest, you get the terrorists to blow up a Walmart and a day care and so forth; if the danger seems real and local, I don't think you'd even have to pay journalists to support you- plenty of people would do it on their own.
Once you have the country in a state of emergency, your politician, who isn't the President, needs to become the President. If he's Secretary of State, all you need to do is bump off the President and VP. If he's not, it's more complicated, but the key is that he needs to be in control of the country when things are maximally broken down. From there it's just a matter of making certain changes to laws, not hard to do with executive power in a time of war, and you have a pretty solid hold on America.
My friend and I considered trying this, but really it would take a lot of money, and you'd need someone to be the politician and we didn't have anyone, and he objected to the idea of blowing up day care centers anyway. I guess I don't really blame him.