This is where Gardner and guns come in. Those two things just might be the key to enacting the legislation, a source inside the credit union industry recently told CU Times. The source is a long-time fixture in the credit union space, who asked to remain anonymous for this story due to the controversial nature of the topic.

Republicans want to outlaw programs such as the Obama Administration's Operation Choke Point, which Republicans contended allowed financial institutions to decide not to do business with controversial businesses, such as gun dealers.

Gardner is considered one of the most vulnerable Republican senators running for reelection. Recreational use of marijuana has been legal in Colorado for more than five years.

And Gardner is one of the two major sponsors of Senate legislation that would provide financial institutions with a safe harbor if they choose to conduct business with cannabis-related firms.

While states have legalized marijuana, it still is illegal under federal law, so financial institutions that serve cannabis-related businesses may face sanctions from their regulators.

If Senate Majority Leader Mitch McConnell (R-Ky.) is convinced that Gardner's campaign needs a shot in the arm, he could place marijuana banking legislation on the Senate's agenda.

"If it gets anywhere, it will be because of Cory Gardner," the credit union source said, adding, "He's in a very tenuous position."

In testimony prepared for the hearing, Rachel Pross, chief risk officer of Maps Credit Union in Salem, Ore., said her credit union decided to serve the cannabis industry to help take large amounts of cash off the street and serve the underserved, which included marijuana businesses.

Maps has $770 million in assets and Pross said it has served the cannabis business since 2014.

This year, Maps has received more than $529 million in cash deposits from marijuana-related businesses, she added.

"The current rift between federal and state law has left credit unions and other financial institutions trapped in a scenario where their mission to serve the financial needs of their local communities is directly pitted against the inability to have perfect information regarding every indirect business activity and the threat of federal enforcement action," she said.

Pross testified on behalf of CUNA, which along with the American Bankers Association has endorsed legislation that would provide financial institutions with a safe harbor if they serve cannabis-related businesses.

In a letter to the Banking Committee, Brad Thaler, NAFCU's vice president of legislative affairs, said the trade group supports congressional efforts to examine how the federal government can provide more clarity to credit unions on the issue.

Thaler said the safe harbor legislation, while not a total solution, would be one step toward such clarity.

Gardner also testified at the Senate hearing.

"In short, the states are leading on this issue, and the federal government has failed to respond," Gardner told the Senate committee. "It has closed its eyes and plugged its ears and pretended the issue will go away. It won't."

Gardner said his state has brought in more than $1 billion in tax revenue from cannabis businesses.

"Last year alone, the state received more than $266 million marijuana taxes," he said. "Millions of those dollars are ending up in Colorado schools."

One of Gardner's constituents from the marijuana industry testified about the problems he has faced.

John Lord, the owner and CEO of LivWell Enlightened Health, a cultivator, manufacturer and retailer of cannabis products in Colorado, said he had to rent out a former bank building so he could store the company's cash.

He also said he has had to travel to the Internal Revenue Service office in Denver with more than $3 million in cash in order to pay the company's taxes.

"Over our 10 years of operations, we have had accounts closed at over a dozen financial institutions," he said.

"In addition, my chief financial officer served on a regional bank's board of directors, and due to his association with LivWell, was asked to resign," he said.

That means that marijuana banking is a major issue in Colorado, where Gardner is running for reelection.

Gardner is only one of two Republican senators running in a state that President Trump lost in 2016; the other is Sen. Susan Collins (R-Maine).

There are 10 Democrats running for the party's nomination.

If McConnell decides that Gardner needs help, he could turn to the marijuana legislation.

And McConnell could sweeten the pot by adding legislation to outlaw Operation Choke Point-like programs to the marijuana bill, which is favored by many Democrats.

Crapo has already hinted at that as a possible compromise. During his recent hearing on the marijuana legislation, Crapo did not provide a direct link, but he opened the hearing talking about Operation Choke Point.

"The Republicans are probably going to enact something to protect industries they like," the credit union community source said.

And there is some precedent for trying to link the marijuana and Choke Point plans.

In the last Congress, the primary House sponsors of marijuana banking legislation, Democratic Reps. Ed Perlmutter of Colorado and Denny Heck of Washington, asked the House Rules Committee to allow an amendment to Operation Choke Point legislation that would have allowed an amendment to link the two.

The Rules Committee, then controlled by the Republicans, rejected that plan.

But it could be revived, and that would give both Democrats and Republicans something they want.

"There's probably a solution out there that can make everybody a little bit happy and everybody a little unhappy," the credit union source said.