According to the model, which was built for The Post by political scientist and Monkey Cage blog author John Sides, Republicans have an 82 percent chance of claiming the six seats they need to move back into the majority. Explains Sides:
The main problem for Democrats is that it’s a midterm year — and the president’s party almost always loses seats in the midterm. Moreover, conditions make it difficult for Democrats to overcome this tendency: The economy is not growing that strongly and, partly as a consequence, President Obama is not that popular. Moreover, as many have noted, many seats that the Democrats must defend this year are in Republican-leaning states.
Given these conditions, the political science literature suggests that quality Republican candidates should emerge. This is because quality candidates are strategic: They tend to run when their chances of winning are higher. Thus, many Republican candidates have significant political experience in state legislatures, the U.S. House of Representatives, and in other offices. (In states where primaries haven’t taken place, we assume that the eventual party nominees will have an average experience level like that of nominees in similar races in the past.)