In the shakeup following her takeover as the president of the Service Employees International Union, Mary Kay Henry has elevated Eliseo Medina to be her second-in command. It's a significant move for America's most politically active union and foreshadows where some of the $50 million the group plans to spend this year will go.

As Harold Myerson explains in a profile, Medina is the foremost advocate for immigrant rights in the organized labor movement. He is credited with leading the voter registration drive in Hispanic precincts of California that helped shift the state's political balance from red to blue over the past decade. He is currently trying to sign up 120,000 new Hispanic voters in Arizona to turn the political tide there.

While Medina (honorary chairman of the Democratic Socialists of America) must still be approved by the union's board, he is already out on a bus tour seeking immigrant voters. And though Medina has complained about President Obama's sluggishness on seeking "comprehensive" immigration reform, Medina's registration efforts and Hispanic outreach was key to Obama's 2008 victories in Nevada and other western states.

Medina's elevation is a big sign that the union sees its membership future and political power among immigrant workers and getting them into the Democratic Party. Expect many of the union's millions to go to changing the makeup of voter registration rolls in battleground states.

Chris Stirewalt joined Fox News Channel (FNC) in July of 2010 and serves as digital politics editor based in Washington, D.C.  Additionally, he authors the daily "Fox News First" political news note and hosts "Power Play," a feature video series, on FoxNews.com. Stirewalt makes frequent appearances on the network, including "The Kelly File," "Special Report with Bret Baier," and "Fox News Sunday with Chris Wallace."  He also provides expert political analysis for Fox News coverage of state, congressional and presidential elections.