Two powerful labor groups combining ahead of the Trump administration

Where it stands: SEIU's 2 million workers will join 12.5 million represented by the AFL-CIO.

• "We think we will be more powerful than ever as joint forces," AFL-CIO president Liz Shuler told Axios Wednesday afternoon.
• This reunion has been in the works for nearly two years, SEIU president April Verrett said. The aim was to build enough power to organize workers and push for pro-labor policies.
• "It's not a reaction to, or a statement about, Trump," she added. But with his return to the White House it is "an affirmation that we're doing the right thing and that now is the time."

Zoom in: SEIU represents many low-wage workers across its three branches — public sector employees, healthcare workers and those in building services (like janitors).

• Many are immigrants, including some who are undocumented and at risk under Trump's proposed deportation policies.
• "It's not just our undocumented or our immigrant workers that are worried about what a Trump administration can bring," says Verrett.
• There are other issues. About half the union's members depend on Medicaid, she said. Republicans have reportedly been considering cuts to the health insurance program to pay for an extension of the 2017 tax cuts.

Zoom out: The AFL-CIO is a huge federation of unions that includes all kinds of workers, from screen actors to teachers to miners. The organization provides policy and politics support to its affiliates — so they can focus on organizing and bargaining.

Flashback: SEIU split off from the group 20 years ago, as the service sector was becoming a bigger part of the economy. The unions' leaders had a pretty tense break-up. (The Teamsters also left the AFL-CIO at the time and haven't come back.)

• At the time, Democrats and union officials worried the schism would weaken the labor movement.

• Though unions have seen a resurgence recently — and SEIU has had some big success, with Fight for 15 in particular — organized labor's power has diminished over the decades.
• The share of the workforce that is unionized is at historic lows.
• "This [reunion] means a more unified labor movement," says Patricia Campos-Medina, a former union organizer who is now executive director at Cornell's Worker Institute.

The big picture: During his campaign, Trump positioned himself as an ally to workers. Teamsters president Sean O'Brien spoke at the Republican National Convention, and he's had some influence on the transition team.

• But both Shuler and Verrett were vocal supporters of vice president Kamala Harris.
• "SEIU would probably have benefitted from a Harris victory, and probably feels more threatened by a Trump administration than most other unions," says John Logan, a labor historian at San Francisco State University.
• Most union observers worry that the second Trump administration will follow the same sort of anti-labor roadmap as the first.

What's next: The unions will formally announce the move on Thursday afternoon in advance of a civil rights event in Austin.

Editor's Note: The headlines of this story have been updated to reflect details on the combination.