WASHINGTON — Senate Republicans united behind Majority Leader Mitch McConnell in insisting that President Barack Obama’s successor fill the Supreme Court vacancy after the death of Justice Antonin Scalia. Democrats looking to reclaim the Senate majority immediately accused them of putting politics ahead of their constitutional responsibility.

Vulnerable GOP incumbents in Pennsylvania, Wisconsin, New Hampshire and Ohio – all states that Obama won twice — echoed McConnell’s contention that the winner of the presidency in November’s election should choose the next jurist. Democrats counter that Obama is president until Jan. 20, 2017, and has every constitutional right to nominate Scalia’s replacement.

“I believe the best thing for the country is to trust the American people to weigh in on who should make a lifetime appointment that could reshape the Supreme Court for generations,” said GOP Sen. Rob Portman of Ohio.

Said Republican Sen. Pat Toomey of Pennsylvania: “President Obama insists that he will nominate someone for the court. He certainly has the authority to do so. But let’s be clear – his nominee will be rejected by the Senate.”

Sen. Ted Cruz, the Texan who has practiced before the high court and is seeking the Republican presidential nomination, has made filling Scalia’s vacancy the centerpiece of his campaign.