WASHINGTON — No longer impeded by Republican blocking tactics, Democrats are on track to win confirmation of up to 88 of President Barack Obama’s top judicial nominations this year, a total that would be the highest for any president in two decades. Last year, Democrats made it harder for Republicans to derail Obama’s nominations by weakening the Senate’s rule on filibusters. So far this year, the chamber has approved 76 federal court of appeals and district court judges, all of them lifetime …