Albert R. Hunt is a Bloomberg Opinion columnist covering politics and policy. He was the executive editor of Bloomberg News, before which he was a reporter, bureau chief and executive Washington editor at the Wall Street Journal. Read more opinion SHARE THIS ARTICLE Share Tweet Post Email

Photographer: Astrid Riecken/Getty Images Photographer: Astrid Riecken/Getty Images

In 2014, Democrats, the majority party in the Senate, had to defend most of the seats up for election, more than a few in unfriendly territory. That year, Republicans took back control of the chamber, picking up nine seats.

Democrats are counting on a similar scenario unfolding to their advantage next year: Republicans currently have a 54-46 advantage, but of the 34 seats up in 2016, only 10 are held by Democrats.

Any outcome depends on unpredictable events over the next 10 months: the presidential race, whether the stronger candidate wins selective primaries, the effectiveness of some challengers, and changing economic or national security issues.

With that critical caveat, Democrats say there’s at least an even chance they will score a net gain of four or five seats. Republicans acknowledge they may lose a couple seats, but believe they will maintain control. This is almost a mirror reflection of the analysis two years ago.

The stakes, while not as high as in the presidential race, are considerable. A new president’s task is made easier when his or her party controls the Senate. (Because of redistricting and population patterns, the odds overwhelmingly favor Republicans retaining their majority in the House, even if Democrats should decisively win the presidency. David Wasserman of the Cook Political Report, the most respected nonpartisan analyst of House elections, estimates that Democrats would have to win the overall House vote by about seven percentage points to pick up the 30 seats necessary for a majority.)

And passage of significant legislation in the Senate usually requires the 60 votes to stop a filibuster by the opposition. But there are important exceptions.

Republicans protested bitterly in the previous Congress when Democrats unilaterally changed the rules to allow action on judicial nominations, except those to the Supreme Court, with a simple majority vote. But given the opportunity, Republicans didn’t reverse that decision this year. Also, there are limited circumstances, under a parliamentary procedure known as reconciliation, when carefully prescribed legislation can be enacted with a simple majority vote.

Moreover, the majority gets to set the schedule, and often the agenda, deciding what legislation to take up and which investigations and inquiries to open.

Last year, Democrats had to defend seats in Republican states such as Louisiana, Arkansas, North Carolina and Alaska; they lost all of those races. This time, half of the seats are in states carried by President Barack Obama, and some of the most competitive are in solidly blue states.

At the moment, Democrats are favored to topple Republican incumbents in two of those states, Illinois and Wisconsin. The only Democratic-held seat that is competitive, as of today, is Nevada where Minority Leader Harry Reid is retiring.

Both sides suffered recruiting failures. The Democrats haven't found a good candidate in North Carolina, while Republicans, so far, have struck out in Colorado and Washington.

The outcome of primaries could shape several contests. Democrats believe that if their preferred candidates emerge in Pennsylvania and Florida, they have a good chance of taking Republican-held seats. And if Senator John McCain gets roughed up by a right-wing challenger in Arizona, that general election could become competitive.

The marquee race may be New Hampshire, where Kelly Ayotte, the incumbent Republican senator and former state attorney general, faces the two-term Democratic governor, Maggie Hassan. That means Granite Staters won't be ignored by the rest of the country after the Feb. 9 presidential primary.

In the fall, the presidential race, with so many independent-minded ticket splitters, may have only minimal impact. There is broad agreement that if a Republican wins the presidency there is almost no way the Democrats could take back the Senate. Conversely, if a Democratic candidate scores a double-digit win, there's little chance Republicans could hold their majority.

There is no consensus, however, that either of those will occur.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

To contact the author of this story:

Albert R. Hunt at ahunt1@bloomberg.net

To contact the editor responsible for this story:

Max Berley at mberley@bloomberg.net