Things only got worse after he assumed office, where, perhaps in the name of bipartisanship, he seldom identified Republicans -- either individual members, or the party writ large -- as the source of the obstruction that's hamstrung his presidency.
With Democrats poised to suffer big losses in November, that's all changing. The Democrats' plan to limit losses requires them to distinguish themselves from the Republicans, who remains unpopular. Hence Obama's the change.
Complicating matters for Democrats is that, well, few Americans know who "Mr. Boehner" is. That might not be the case if Obama had given speeches like this starting a year ago. But there are still several weeks to go until election day.