The Marketplace Fairness Act is in short a national sales tax on online purchases (that is an extreme layman’s view).  See the full run down at Breitbart.

The List of Republicans supporting this bill are:

Gov. Bentley Ala.
Gov. Branstad Iowa
Gov. Christie N.J.
Gov. Daniels Ind.
Gov. Haley S.C.
Gov. Haslam Tenn.
Gov. LePage Maine
Gov. Sandoval Nev.
Gov. Snyder Mich.
Former Gov. Barbour Miss.
Former Gov. Bush Fla.
Sen. Alexander Tenn.
Sen. Enzi
Sen. Blunt Mo.
Sen. Boozman Ark.
Sen. Corker Tenn.
Rep. Ellmers N.C.
Rep. Pence Ind.

Hattips & Shameless plugs:

Breitbart.com
@TreeTreeTweeTs

Check out RINO List 2012 for $3.97 on Kindle 
Also, check out the paperback for $7.97