The change was welcome for Democrats looking ahead to a close election.
“Until very recently, the border was President Biden’s problem almost exclusively,” said Geoffrey Garin, a Democratic pollster. “But now by blocking strong, bipartisan border legislation Republicans have made it their problem as well.”
He added, “The fact that President Biden can now say that he was prepared to sign and enforce the strongest border law in history, but Republicans blocked it at Trump’s behest puts Biden in a much better position than he was before in the immigration debate.”
Margie Omero, another Democratic strategist, said voters would understand which side actually wanted to get something done. “Joe Biden and Democrats in Congress are working for solutions,” she said. “The Republican Party routinely puts obstruction and scoring political points over tackling our big challenges.”
Mr. Biden’s critics, though, doubt he can shift blame after so much time. For much of his presidency, they said, the president and his allies have resisted even admitting there was a crisis, only to switch gears and say that there is one and that it is Mr. Trump’s fault.
“It seems to me absurd on its face,” said Mark S. Krikorian, the executive director of the Center for Immigration Studies and a leading voice for tougher policies. “Obviously Biden partisans will latch onto that, and obviously Trump partisans will scoff at it. The question is will people in the middle buy it or not. I find it hard to believe that anybody would believe it. After three years?”