If a strong majority of American citizens support a reform that potentially could save untold numbers of lives, then wouldn’t it be logical for Congress to act?

This Congress, however, defies logic.

The bill that 90 percent of Americans want would close a gaping loophole in background checks for gun purchases. Anyone wanting to buy a gun from a federally licensed dealer must first pass a FBI criminal background check. The loophole is that no background checks are required for private sales, such as at gun shows.

U.S. Sen. Chris Murphy estimates that as much as one-quarter of gun sales in this country occur without criminal background checks. Hoping to change that, Murphy introduced the Background Check Expansion Act before the Senate on Wednesday with several co-sponsors.

This bill makes sense. It is not an entirely new regulation, which should mollify gun-rights advocates; it simply expands what has existed for years.

In 1993 the Brady Handgun Violence Prevention Act established the National Instant Criminal Background Check System for guns bought through licensed dealers. Private sales were not included at that time, unfortunately. That was before internet sales became widespread.

The expansion bill compromises by allowing exemptions, such as guns transferred between family members. A bill without that compromise failed in the Senate last year.

The criminal background check system works, for the most part. Last year 12,000 people were stopped from purchasing guns because the check uncovered a criminal history, Murphy said.

We believe the bill should go further, or another one be adopted, to close the Charleston loophole. Now, if a licensed gun dealer does not get a response from the FBI on a background check within three days, the sale can go through on the fourth day. Most checks clear within minutes, but because of missteps the 72 hours had lapsed and Dylann Roof in 2015 was able to buy a .45-caliber handgun — even though his felony drug charge should have blocked the sale. Roof used that gun to kill nine people in a Charleston, South Carolina, church.

Gun sales should not proceed until the criminal background check is cleared.

No one measure, such as expanding background checks, can prevent every death by gun. At the beginning of this month, 58 people were shot to death at an outdoor concert in Las Vegas and hundreds more injured by a shooter who legally owned his weapons. The new bill could not have stopped the massacre, nor could it have prevented the Sandy Hook tragedy of 2012.

No single measure can halt the exchange of illegal weapons.

But making criminal background checks universal can help keep guns out of the wrong hands.

Since the Sandy Hook Elementary School shooting, more than 1,500 mass shootings with ever-escalating death tolls have erupted. Guns kill nearly 90 Americans a day, according to the Newtown Action Alliance.

Tell Congress it is unacceptable to do nothing to curb the carnage.