By WILL WEISSERT
WASHINGTON (AP) — Activist groups want to push the Democratic Party in Congress to the left by notching midterm primary election wins that replace establishment, moderate incumbents with progressive alternatives. Many see Rep. Henry Cuellar, a long-serving conservative Democrat from south Texas, as a good place to start. He’s facing a rematch with a progressive challenger he narrowly defeated two years ago. They are hoping that FBI agents carrying out a search near Cuellar’s home barely six weeks before his state’s March 1 primary makes him all the more vulnerable — potentially tilting his second primary battle with progressive immigration attorney Jessica Cisneros in her favor.