While Lincoln's career is on the line Tuesday, organized labor's influence is on the ballot as well.

From The Washington Post:

If the defeat of Sen. Bob Bennett (R-Utah) at his state party convention last month was an uprising of the conservative grass roots, and the loss three weeks ago by Sen. Arlen Specter (D-Pa.) revealed the perils of a party switch, then the runoff fight that Sen. Blanche Lincoln (D-Ark.) faces Tuesday is indicative of what happens when you cross a major -- and majorly well-funded -- interest group.

Ostensibly, Lincoln's opponent is Lt. Gov. Bill Halter. But the practical reality is that she is running against a handful of major labor unions -- the Service Employees International Union and the American Federation of State, County and Municipal Employees, to name two.

In a memo sent to reporters Saturday, Lincoln campaign manager Steve Patterson said that unions had spent more than $10 million on the race . . . .

Bill Clinton, a Lincoln supporter, has gotten in on the act as well, appearing at a Little Rock rally last week and now in a television commercial in which he decries the influence of national unions on the race. "This is about using you and manipulating your votes," the former president says.

Labor is decidedly unapologetic about its involvement, insisting that Lincoln's apostasy on the inclusion of the public option in the health-care bill as well as her opposition to the Employee Free Choice Act signaled that she was no longer with the party on its core principles.

There is cautious optimism within labor's ranks about Tuesday's result. Predicting primary turnout is tough and predicting runoff turnout is next to impossible, but according to one senior union official, the outcome is almost beside the point, because a message has been sent to the entire Democratic caucus. "We have already heard from other senators on the Hill that Lincoln was reasonable on financial reform because of this fight, and two progressive senators have told union lobbyists that they need to do more of this to keep moderate Dem senators 'in line.' "

Given Lincoln's dire electoral straits, it's hard to imagine that other moderate Democratic senators, such as Ben Nelson (Neb.) and Mary Landrieu (La.), won't be watching their votes a bit more carefully for fear of being the next chapter in a newly aggressive union strategy toward Democrats.

That mentality has rubbed raw some Democrats, who wonder why labor is spending so much money to help elect a candidate who, if polling is to believed, would start at a significant disadvantage to Rep. John Boozman (R) in the general election. (To be fair, polling also shows Lincoln trailing Boozman in Arkansas -- which voted heavily against Barack Obama in 2008 and has grown increasingly opposed to his agenda, and his party, during his first term.)

While Lincoln's career is on the line Tuesday, organized labor's influence is on the ballot as well. Lose this race, after the millions spent and the manpower devoted to it, and unions will find themselves answering a slew of questions about whether their political influence is flagging.