the fall of the Roman Empire or the Roman Republic?

I've heard Pat Buchanan interviewed a few times in the past couple of days. He's got an alarmist new book out about illegal immigration. I say "alarmist" even though he might be spot on. He was drawing an analogy with the fall of the Roman Empire where barbarians streamed across the Rhein and the Danube and the Roman authorities did nothing to stop them. For sure we need to stop the flood of illegal immigrants across the border. A trickle of illegal immigrants we could deal with, but a flood, no. What I was thinking of though was that our situation might be more analogous to the last days of the Roman Republic. At that time there were figures that came to power as dictator, first Sulla and later Caesar. Both assumed power at times of crisis and both promised to restore "the old republic". Sulla did ultimately retire and turn power back to the Senate and the consuls, but Caesar never did and, of course, was assassinated by the Senate. The Left in this country talks alot about George Bush "acting like a king", but I think that's so much B.S. I worry though what would happen if a democrat became president, because I think those guys have less concern for the Constitution and the rule of law than Republicans do. Just look at how much respect New Jersey democrats had for state laws when Robert Torricelli dropped out of the Senate race some years back and the democrats appointed Frank Lautenberg even though state law clearly stated that the deadline for such a manuever had passed. Or look at how the Clintons used the power of the presidency for their own personal advancement and the way Clinton abused the power of the pardon in his last days in office (Marc Rich anyone?). Well... just something to think about.