Here is a background of how the fund got started. It mentions a paper by Michael Ferguson and Hugh Douglas Witte that look at the "Congressional Effect." These are some pretty heavy lines:
"Since 1897, the year after the Dow was created, an impressive 90 percent of gains came on days when Congress was out. [Ferguson and Witte's] charts show that a dollar invested in 1897 that was converted to cash every time Congress met was worth $216 by 2000. The opposite strategy — investing only when they were in session — only got you $2 by 2000."
Here's another bit on the fund.
The Singer Congressional Fund gets the TPS Seal of Approval.