Washington (CNN) - Incumbent Sen. Blanche Lincoln is pulling out the big guns in her bid to defeat a hard charging challenger in the Arkansas Democratic Senate run-off.
Now just four days away from her showdown with Arkansas Lt. Gov. Bill Halter, Lincoln's newest campaign ad features former President Bill Clinton – the favorite son of Arkansan Democrats.
The two-term senator is locked in a tight run-off with Halter after neither candidate cracked the 50-percent mark in the May 18 primary.
Clinton made an appearance with Lincoln at a campaign event last Friday in Little Rock, and the new 30-second spot features video of Clinton quoting from a Washington Post article that said that national labor unions had decided to make Lincoln "the poster child for what happens when a Democrat crosses them."
Titled "The President," the ad closes with Clinton telling the crowd that "if you want to be Arkansas' advocate, vote for somebody that will fight for you."
Lincoln has been targeted extensively by labor unions during her re-election bid, though she has fought back by portraying unions as Washington-based outsiders interfering in Arkansas politics.
Many of the labor unions that are trying to defeat Lincoln now have supported her in the past. Among the issues labor unions cite her opposition to the Employee Free Choice Act, which unions strongly support.