And last week, a companion to the bill was introduced with 17 co-sponsors in the House for the first time, a procedural measure that signaled support for RESA.

Notwithstanding that development, concerns in the House over some of RESA's provisions have stalled the bill's progress, said Will Hansen,  senior vice president of Retirement and Compensation Policy for the ERISA Industry Committee, which advocates on behalf of large plan sponsors.

A draft of the House version of the omnibus will be released as early as midnight Tuesday, with that chamber expected to vote on the bill Thursday.

"I'm hearing that it is unlikely RESA will get included," Hansen said. "The Senate has it as one of its top priorities, but the House is debating whether they want to have their own formal mark up of the bill. But you never know until the text is released."

Previous retirement legislation, like the Pension Protection Act of 2006 and the Multiemployer Pension Reform Act of 2014, had bipartisan, bicameral input from both chambers of Congress, Hansen noted. "But it's Congress. You never know. New precedents can be set."

Geoff Manville, principal, government relations at Mercer, also said RESA's chances of passing in the omnibus are not good.

"It's looking like a heavy lift," Manville said, regarding his conversations with staffers in the House.

"The Senate is all in—it would pass RESA by unanimous consent in a heartbeat," he added.

But some members in the House—specifically on the Ways and Means Committee—have concerns over the bill's lifetime income disclosure provisions and a pay-for in RESA that would eliminate so-called stretch IRAs.

"It's less a disagreement about substance, and more about process," said Manville. "Ways and Means would like to take some time to move the bill through the committee process, and give it a full airing on some of the issues they'd like to change."

The ERISA Industry Committee has been a vocal supporter of RESA, but has also asked lawmakers to strike the Lifetime Income Disclosure Act provision in it.

LIDA, first introduced in 2009, would require sponsors and administers of defined contribution plans to provide participants with an estimate of lifetime income streams based on savings. The income assumptions would be based off guidelines from the Labor Department.

The concept would be to motivate higher savings rates. While LIDA has had bipartisan support in both chambers of Congress, ERIC has raised concerns over the bill on behalf of plan sponsors for years.

"There are a lot of assumptions built into calculating what would be government mandated assumptions," said Mr. Hansen. "So they wouldn't apply to every person's individual circumstances."

The good intention behind the disclosures would create confusion for plan participants, and costs for sponsors, said Hansen.

Participants may interpret the estimate as an actual annuity payment, even in plans that don't offer annuities, he said.

And sponsors would have to revamp plan communications to include a new disclosure that explains how the income assumptions are arrived at, and disclose that the assumptions could vary substantially from what savers actually accrue.

"That adds to more confusion for plan participants, and it would drive up costs for our members," explained Hansen. "We don't want to have an external party mandate an income figure on a communication that is strictly between an employer and employee."

RESA would reportedly be paid for, in part, by eliminating so-called stretch IRAs, which are used in estate planning to extend the tax-deferred status of IRAs when they are bequeathed to non-spouse beneficiaries.

Previous attempts to eliminate stretch IRAs have been scuttled by Congress.

"That pay-for is raising some objections," Manville said.

One possibility is that components of RESA could be broken off and added to the omnibus, but  Manville suggested that is unlikely.

Another possibility is that the House gets motivated to introduce the bill in committee later in the 115th Congress. But that prospect is also questionable in an election year with a divided legislature negotiating an already loaded agenda.

"It's not at all clear what happens if RESA isn't part of the omnibus bill," Manville added.