Stupid question: what real world impact does contempt of Congress carry? Is it toothless and will be ignored or does something tangible happen?
One civil contempt and the other criminal contempt.
The contempt charge negates Holder's ability to represent the DOJ in court. It's a vote of no-confidence. It also allows congress to appoint an "independent" investigator/prosecutor of their choosing to investigate the case. That is, if employed, it would take the whole investigation out of the DOJ's control. If they continue to stonewall or obstruct the independent investigation, the independent investigator/prosecutor can file charges against Holder.
However, the President's Executive Privilege stance now must be investigated first. The whole process will take years and will fall out of the news cycle long before November.
I believe that was the strategy behind Obama claiming executive privilege. It will only become a problem for the president after the election and likely will go away after he is unseated.
So, yes there are some teeth if they continue to press. But Holder will not go to jail and/or implicate Obama before November.