On the eve of a vote that could cripple unions throughout the state of Michigan, President Obama visited a Detroit-area automotive plant to tout their importance.

Speaking during a stop at Daimler's Detroit Diesel plant, Obama announced a $120 million investment by Daimler that is expected to create 115 jobs. He also denounced right-to-work legislation that state lawmakers are expected to approve Tuesday in Lansing.

"These right-to-work laws have nothing to do with economics and everything to do with politics," the president told a cheering crowd, according to the Detroit Free Press. "What they are really talking about is giving you the right to work for less money."

The right-to-work legislation would make it illegal to require new employees to make financial contributions to a union as a condition of their employment. Workers who do not pay dues would nonetheless be eligible for the same wages and benefits bargained for in a union contract.

Republican Gov. Rick Snyder is expected to sign the legislation, which would make Michigan the 24th state to approve a right-to-work law. He has said the law would give Michigan a more competitive business environment.

On Monday, members of the United Auto Workers wore stickers during Obama's visit, saying, "The President Saved The Auto Industry. Don't Let Snyder Destroy It."

Obama used the outing, his first in Detroit in more than eight months, to tout his economic plan to raise tax rates on households that make more than $250,000 two weeks before a key deadline arrives.

Detroit Diesel will invest in new equipment that makes engines, transmissions and axles at a single factory, which will help streamline Daimler's operation. Daimler was one of the companies rescued by Obama's use of federal funds to bail out the American auto industry during the depths of the recession.

In pitching his plan before the cheering audience and in admonishing Synder, the president said, "Our economic success has never come from the top down. It comes from the middle out. It comes from the bottom up."