"The Main Street Individual Fund -- a 527 group that has a similar views and goals as the pro-moderate, anti-conservative Republican Main Street Partnership -- announced Tuesday it would be spending $200,000 over the next two weeks to help Specter."
The NRO article cites two different groups supporting Specter. The Main Street Individual Fund took a large donation from Soros.
http://www.nationalreview.com/geraghty/geraghty200404140840.asp <-- Link
"The Republican Mainstreet Partnership, a group of lawmakers who often vote against bills backed by President George W. Bush, raised a record amount of money in the first quarter, helped by current and former executives of Goldman Sachs Group Inc. ...
" The 64 congressmen belonging to the partnership, including Pennsylvania Senator Arlen Specter, have bucked Republican leaders by voting with Democrats on their opposition to Bush's tax cuts and their support for spending more on the environment and health care. Republicans control the Senate with 51 of 100 votes and the House with 228 of 435 seats, which often can give the Mainstreet Partnership lawmakers a decisive bloc of votes."
That is from the Bloomberg article that you noted, and describes an alliance of legislators acting as a bloc.
http://quote.bloomberg.com/apps/news?pid=10000176&sid=aQjUh6DohVYY&refer=us_elections <-- Link