Out of 12 it is - it's 25%. The GOP only had 12 seats held by Republicans up for re-election - they lost at least 25% of them and maybe 33%.
That is huge. The House had about 220 republicans up for re-election and lost about 20 of them. That is only 10%.
The Senate took a much bigger hit than the House.
Its all just a numbers game and we still might retain the senate. Remember VP Cheney has a vote.
They may have taken a bigger hit percentage-wise, but if we hold the senate, it's really a much smaller hit. The control and committee chairs are more important than the percentages. Control and chairs are real world; the percentages are an abstraction.