White House senior adviser Dan Pfeiffer doesn't understand why Congressional support for universal background checks for gun purchases is waning.

"I've been in politics a long time," he said at Politico's Playbook Breakfast Wednesday. "I very rarely run into a 90-percent issue. … Universal background checks are a 90-percent issue."

Ninety percent of Americans supported background checks for all gun buyers in a February 2013 Quinnipiac University poll. A poll released Thursday by the same group showed that 91 percent of registered American voters support background checks.

The Obama administration has moved to pass new "common-sense" gun control measures. The new legislation has hit a wall in Congress, with key lawmakers taking issue with closing the loophole extended to private gun vendors. The loophole stipulates that private gun sales, like those at gun shows, do not require background checks.

The NRA, which previously supported expanded background checks, announced after the Sandy Hook Elementary school massacre that it opposed the checks, arguing that the current system is ineffective. Some key senators have now backed away from the initiative in fear that supporting it could carry hefty political consequences. This has come as a surprise to those who thought the gun-control measure would surely pass in light of the tragedy.

Two weeks ago, New York Mayor Michael Bloomberg launched a television ad campaign on the importance of the background checks meant to target 13 key senators needed to pass the law.

When asked why congressional support for the initiatives has wavered, Pfeiffer told Politico's Mike Allen, "There may be people in Washington who certainly might be getting cold feet here, [who] are looking for a way out of making progress here."

But Pfeiffer predicted the current situation would ultimately hurt lawmakers.

"People feel very strongly about this," Pfeiffer said. "There aren't a lot of cardinal rules in politics, and one is, You don't want to get on the wrong side of a 90-percent issue."

President Obama, who traveled to Colorado on Wednesday, is visiting regions affected by gun violence in hopes of rallying support for his gun-control measures.

"What the president wants to sign is the strongest gun bill he can sign," Pfeiffer said, "and our baseline here is … what is the law today, and how much stronger can we make it."