Greenspan, fully aware of the effects of the economy on Presidential elections, increased the federal funds rate in 2000 (making a Bush election over Gore more likely) and then lowered the Fed funds rate in 2004 so that Bush would be reelected. The evidence is in the timing of fed fund rate changes.
Note the years in blue which are election years, and the years in yellow which are the year after. In 2000 Greenspan was making the economy more difficult in order to defeat the Democrat. In 2004 he was making it better to elect the Republican.
In 2005 Greenspan knew that the low interest rates had created the housing bubble, so he was trying to stop the bubble. The continued into 2006. Greenspan was still trying to correct the problems he had created in 2001 through 2004. In early 2007 CountryWide, the nations' largest mortgage lender, announced in early Spring that the collapse of the housing bubble was causing economic problems. The result was the credit crunch that became obvious to everyone by Summer 2007, but which they thought could be isolated in just the mortgage markets. We now know that was living in a fool's paradise.
Intended federal funds rate 1997 to present