If confirmed, she would be the first African American woman on that court, which sits in Philadelphia.
But Toomey questioned her qualifications, said the White House knows he does not support her, and said the administration had chosen a "confrontational approach" over a long-standing practice of cooperation when it comes to federal judges from Pennsylvania.
"Instead of blowing up a bipartisan working arrangement," he said in a statement, "the president should take a step back, put an end to this political theater, withdraw a nomination that is not suitable for such an important lifetime position."
Every other judicial nominee during his tenure had been OKd in advance by him and his Democratic counterpart, Sen. Robert P. Casey Jr., Toomey said. Such arrangements are often used in states with senators from opposite parties.
A fight, though, just might suit Democrats.
Toomey has been one of their prime targets as liberal activists try to pressure Republicans into giving a hearing to an expected Obama nominee to the Supreme Court. That pick could come as soon as this week.
Democrats have also cast Toomey as a far-right senator unwilling to compromise as he faces a tough reelection fight this year.
They spent months last year battering him for, in their view, stalling a Philadelphia judge, Luis Felipe Restrepo, nominated to the same court. Toomey said he backed Restrepo, but the wait angered Hispanic groups and others.
Haywood, 47, would replace Judge Marjorie O. Rendell, who took senior status in July.
Casey urged Haywood's confirmation in almost the same words he used hours earlier in pressing the GOP to give fair consideration to an Obama Supreme Court nominee. Republicans should give Haywood "a fair hearing and timely vote," Casey said in a news release.
Conservative groups, though, have urged Republicans to block any further Obama judicial nominees.
With the GOP controlling the Senate, public pressure is the only leverage Democrats have.
Toomey said Haywood "struggled to answer legal questions" about Obama's executive actions blocking deportations of some illegal immigrants - moves that angered conservatives.
Haywood, an Allegheny County native, has been nominated to the court that hears appeals of federal cases from Pennsylvania, New Jersey, Delaware, and the U.S. Virgin Islands.
That court now appears set to be another battleground in the fight over the judiciary.