A sense of duty has not propelled the  Republican leaders of the U.S. Senate to act on President Obama's nomination of a U.S. Supreme Court justice. But even if patriotic and constitutional responsibility were not enough to move them, maybe something they hold dearer will force their hands — political expediency.

The nightmare has come true for the Republican establishment. Donald Trump is the presumptive presidential nominee of the GOP. While some early polls offer false hope of a competitive general election race, the fact is that Trump’s lack of support among Latinos, African-Americans and women make it highly unlikely he will win.

Senate Republicans should act now on the nomination of appeals court judge Merrick Garland to fill the Supreme Court vacancy created by the death of Justice Antonin Scalia. Garland has a record of moderation as an appeals court judge. At age 63, he will not spend decades on the Supreme Court.

In 1997, when confirmed as an appellate judge, Garland received strong backing from both parties, including from seven Republicans still serving in the Senate.

Majority Leader Mitch McConnell has said the next elected president (not the current one, for some reason) should get to fill the vacancy that has left the Supreme Court stuck with a 4-4 split in some cases.

But given that former senator and secretary of state Hillary Clinton will likely be that next president, McConnell and others in Senate leadership positions might want to reconsider. Clinton would be under no obligation to stick with Garland as the nominee. She could opt for a younger jurist with a more progressive appellate record.

And, with Trump at the top of the ticket, a Democratic majority could be in place in the Senate next year to act on a Clinton nomination.

Sen. Jeff Flake, Republican of Arizona, is among those in the party calling for pragmatism.

"If we come to September and ... it doesn't look promising, then we may want to reconsider," he told the New York Times.

Good advice, but why wait until September?

Swallow your pride, Sen. McConnell, and move the Garland nomination forward.