At least Speaker of the House John Boehner made excuses when he skipped the memorial service in Tucson last week:
... on the heels of renewed calls for bipartisanship and toned-down political rhetoric, Boehner is saying “thanks, but no thanks” to another offer to appear at an event with the president – Wednesday’s White House state dinner.
But hey, Boehner is probably pretty busy pretending he's going to repeal health care reform and replacing it with nothing, not to mention the Republican's ongoing efforts to avoid coming up with an agenda of any kind. Throw in the White House's strict no-smoking policy and you can appreciate why Boehner will be busy that night.