[Firehouse]

Your Greek Life advisor is correct: there is some general correlation between periods of fraternity/sorority systems' strengthening and weakening, and whether a Democrat or Republican President is in office. However, I can't determine - and I don't think anyone else has done so either - what factors go into making that happen.
Here are the cycles: 1948 (post WWII) through the 1950's Greeks were very strong. Democrat Truman was President for the first four years, then Republican Eisenhower till 1960. Truman was moderate, Eisenhower was conservative.
1960-1970: Greeks were still very strong, but with clouds on the horizon. Conservative Democrat Kennedy then liberal Democrat Johnson were Presidents. Conservative republican Nixon elected in 1968.
1970-1973: Very, very bad time for Greeks. Republican Nixon was re-elected then resigned. Nixon was a conservative, but the social vectors were already in place to bring the Greek system down. Under conservative Republican Ford (1973-1976) and liberal Democrat Carter (1976-1980) things improved somewhat, but the damage of the late 60's/early 70's was hard to overcome.
The 1980's under conservative Republicans Reagan and Bush I saw a fabulous Greek renaissance. The 1990's under liberal Democrat Clinton saw another crash of the system.
Beginning in 2000, which coincides with the election of conservative Republican Bush II, Greek numbers are rising again strongly across the country.
As for an explanation, I have no idea. Maybe it has to do morewith conservative vs. liberal rather than Republican vs. Democrat.