Campaign junkies: A team of political scientists at the University of California, Davis, gives the Republicans a 54 percent chance of taking control of the Senate this year.

The forecasters view four Senate races as key to the majority. "Our model suggests, in fact, if Republicans win the Senate elections in only four states -- Alaska, Louisiana, Iowa, and Montana -- then they are very likely to take control of the chamber," they write on the Washington Post's website.

That's a surprising mix of races, perhaps.

Montana, for instance, is an open seat that seems likely to go Republican, leaving the focus on other elections (the Montana race is leaning red). But there's a wild card: Retiring Democratic Sen. Max Baucus just became U.S. ambassador to China and his likely Democratic replacement may have a leg up in November as the incumbent.

In Alaska, Democratic Sen. Mark Begich still holds a slim lead over possible challengers, and Democrats have an edge over Republicans in Iowa's open seat race. But incumbent Louisiana Democrat Mary Landrieu appears to be in trouble.

"Of course, the Republicans could lose all four of these elections and still gain control of the Senate by winning a different set of four," they write. "Our point is that any other four pose more difficult challenges than these four. (The next three in line are Michigan, Arkansas, and North Carolina)."