The U.S. Chamber of Commerce has a message for Republicans stalling on immigration reform: Shape up, or good luck on your own in 2016.

Chamber President and CEO Tom Donohue, a reliable supporter of key conservative election races and issues, said the GOP might as well sit out the 2016 presidential elections if they don’t tackle immigration reform this session.

“If the Republicans don’t do it, they shouldn’t bother to run a candidate in 2016,” Donohue said at a panel Monday on America’s infrastructure. “I mean, think about that. Think about who the voters are.”

The Republican Party has already acknowledged its crucial need to diversify its base after President Obama swept the 2012 elections by eye-popping margins with Latino voters. Republicans in the Senate scrambled last year to hash out a bipartisan immigration deal that easily swept the upper chamber. But reform efforts are currently held up in the Republican-led House, where lawmakers have indicated they won’t be taking up the issue very soon.

The Chamber has made immigration a prominent focus, signalling to Congress that “failure to act is not an option.” The group played a large role in the Senate bill by bringing together big business and labor last year, striking a deal with the AFL-CIO on a low-skilled worker program.

“I do believe that we’re absolutely crazy if we don’t take advantage of having passed an immigration bill out of the Senate,” Donohue said. “Because going back and doing it again might be harder.”

The Chamber president said he was confident that Congress could get reform done by the end of the year.

“Do something rational in the House and put it together, and let’s get the three or four things we really need there,” he said. “And we’ve got a lot of heat on that and we’re going to put a lot more.”