Democrats likely to retain Senate as four critical races shift in their favor (Originally posted on Yahoo!'s "The Signal" Blog)

After weeks in which the fate of the Senate simmered at nearly even odds of flipping for Republicans or remaining in Democrats' control, the outlook has shifted dramatically in the Democrats' favor. The incumbent party now has an 80 percent chance of retaining its majority, according to the Signal's prediction model.

The break is largely due to critical races in Missouri, Wisconsin, Massachusetts and Virginia, all of which have favored the Republican at some point in the past month and now favor the Democratic candidate.

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