“We passed a budget. It is the President/Harry Reid who is shutting down the government by ignoring it.”
Put the shutdown on them for NOT acting when the House has acted (or for issuing a veto if somehow the Senate comes along).
If you want to add a talking point, then:
“The country voted in November to stop this runaway spending. We listened to votes. Harry Reid and President Obama continue to ignore the voters.”
Really what more is there to the messaging here? Keep it short, to the point and repeat, over and over and over. Period.