Question about Karl Rove

When I did my stint in the Senate, it was a serious no-no for any Senate staff to work on ANYTHING campaign related while on the Senate clock.  Apparently, it's illegal for taxpayer dollars to support campaign activities.

Are the rules different in/for the White House & its staff?  I ask because virtually every news story about Karl Rove mentions that his new job is to work 100% on the November campaign.  If anyone knows why it's OK for taxpayer dollars to pay Rove's salary to be a political consultant for the Republican Party, please let me know.