How thorough are the safeguards against foreign countries contributing to US Presidential candidates?

Well, knowing that those safeguards are put in place by the very people that would be receiving the money (i.e., politicians) it probably is something to always be watching and could never truly be thorough enough...and Greed/Power/Ego isn't party specific from my observations over time, so keeping an eye out on both parties over abuse is certainly a worthwhile thing to do.