Senate Control Boiling Down to Five States

Stuart Rothenberg August 10, 2012 · 1:00 AM EDT

The fight for the Senate gives every indication that it will go down to the wire, with enough races still in play in late October so that neither party can feel completely confident about its prospects.

Right now, control of the Senate appears to rest on the outcomes in five states - four of them held by Democrats - Montana, North Dakota, Virginia and Wisconsin - and one of them by a Republican - Massachusetts.

Assuming that Republicans take the Nebraska and Missouri Senate seats and Democrats finally win back a Senate seat in Maine, the GOP will need to win four of the five seats that will decide control of the Senate for two more years.

Other seats certainly could be in the mix - Florida and Nevada look the most likely - but the five states now seem to be the most likely to determine control. And strategists on both sides of the aisle have a harder time imagining Ohio, New Mexico, Hawaii, Indiana or Arizona flipping parties, though those states certainly are worth watching as some of the underdog candidates in those states are running strong races in generally unfriendly territory.

Florida and North Dakota are moving in different directions in our ratings, but for very different reasons.

In North Dakota, polling shows the race extremely close. Heidi Heitkamp (D) continues to be personally popular - more popular than Republican Rep. Rick Berg. And while Republicans believe that Mitt Romney's expected blowout win in the state should help drag Berg across the finish line ahead of his Democratic opponent, they no longer underestimate the challenge facing their nominee.

In Florida, Rep. Connie Mack (R) continues to run well against incumbent Sen. Bill Nelson (D). While Democrats continue to be confident that Nelson's advertising will open up a more comfortable margin over Mack, the Republican's competitiveness reflects the state's competitiveness.

Wisconsin remains something of a conundrum. Republicans seem optimistic that the winner of Tuesday's primary in Wisconsin will have an advantage over Rep. Tammy Baldwin, the Democratic nominee. Democrats are more optimistic about the congresswoman's chances, no matter who the GOP nominates.

Massachusetts is still one of the premier national contests. It remains close, and voters will have to decide whether they are willing to re-elect a Republican while also voting to re-elect Obama with a solid majority. The key to that contest may well be whether Sen. Scott Brown (R) can attract the 20 percent of Democrats he needs to win a full term.

The presidential contest could well determine control of the Senate.

If swing voters turn to Romney in the final weeks of the campaign, they could also turn to George Allen in Virginia, Denny Rehberg in Montana and Berg in North Dakota, improving the GOP's chances of netting the three seats they need if Romney wins the White House. But if Romney fades, it is more difficult to imagine Virginia and Wisconsin voting for Obama for president and for a Republican for the Senate.

For now, the most likely outcome in the fight for the Senate seems to be a GOP gain of one to four seats, which means control remains a toss-up.