The Senate may be having a tough week — but the House may well be about to have a tougher one. Lawmakers expect to return to Washington Monday with already lapsed government funding and a Senate-struck bipartisan deal, leaving them remarkably little margin of error to stave off a true shutdown. There are potential problems on both sides of the aisle: Many Democrats are wary of extending Department of Homeland Security funding, even temporarily, without any new restrictions. Republican hardliners don’t want to put off funding DHS for a full year — and especially not by funding it for just two weeks. And still others are treating their second bite at the package as a fresh opportunity to tack on their own priorities.