A major labor group kicked off its effort early to get out the vote to unseat incumbent Sen. Blanche Lincoln (D-Ark.).

The AFL-CIO launched a get-out-the-vote effort targeting early voters on Tuesday in support of Arkansas Lt. Gov. Bill Halter's bid to unseat Lincoln in a Democratic primary runoff election.

A spokesman for the union said they believe that an aggressive turnout effort — using leafleting, phone banking and canvassing — would be key in defeating Lincoln in next Tuesday's election.

Unions including the AFL-CIO have spent aggressively in favor of Halter's effort against Lincoln. Those efforts in part helped keep Lincoln under 50 percent in the initial May 18th primary, which forced the runoff election. In that primary, Lincoln won 44.5 percent of the Democratic primary vote, while Halter won 42.5 percent.

Both Halter and Lincoln have ramped up their advertising and turnout efforts in early voting, and Lincoln has at times hit back hard against organized labor, emphasizing her independence in political ads.

For their part, AFL-CIO's pamphlets portray Halter as on the side of workers, while painting Lincoln has having "left working families behind." Some 90,000 of these pamphlets are being sent to Arkansas, with more to come.

The winner of the runoff primary will face Rep. John BoozmanJohn Nichols BoozmanOvernight Defense: Top general defends Afghan war progress | VA shuffles leadership | Pacific Command gets new leader, name | Pentagon sued over HIV policy Senate panel unanimously approves water infrastructure bill Senate GOP urges Trump administration to work closely with Congress on NAFTA MORE (R-Ark.) in a top-tier general election battle.