As Senate Democrats consider a change to the rules to restrict filibusters, there's a nagging concern in the back of their heads: What happens when we become the minority party? 2014 is looming increasingly large in Washington, given the possibility that next year's elections will finally shift a balance of power that's settled firmly into place.

Politico writes that Monday's vote on Robert Wilkins, President Obama's nominee to the D.C. Circuit Court of Appeals, will be blocked by Republicans — not a surprise, given that the Republicans have blocked two previous nominees to the court this month alone. The appeals court, responsible for weighing in on a broad swath of federal legislation, is a focal point of tension in the Senate, with fights over its nominees (in Politico's evocative words) sending the Senate "careening down a path toward yet another war."

But there's only ever been one war: a historical recreation of the long, brutal battles of World War I. And Washington's entrenched positions — a solidly Republican House, a Democratic Senate and White House — are unlikely to change before 2016. The president's not going anywhere and, mustered enthusiasm from Minority Leader Nancy Pelosi aside, the Republicans' 31-vote majority in the House isn't going to budge in 2014, the sort of off-year election that almost always benefits Republican candidates. It's the Senate that plays the role of Verdun in this little recreation of World War I — and the four possibilities of what happens after next year's 35 Senate races will have a significant effect on the final two years of the Obama presidency.

We can predict the results of most of those races well in advance — as we did in July. Twenty-one Democratic seats are up, as are 14 Republican seats. Seventeen of those races, as Nate Silver predicted over the summer, will almost certainly be won by Republicans, a net gain of three seats right off the bat. It's conceivable — unlikely, but conceivable — that the Republicans could do much better than that, picking up a filibuster-proof majority.

On Sunday, Politico's James Hohmann outlined a number of the races, suggesting that a dramatic shift is unlikely, and pointing out that this is the third-straight cycle that the Republicans might have taken the majority. Each of the past two times, the party has been stymied by the nominations of far-right candidates that went on to lose the general election: Sharron Angle, Richard Mourdock, Christine O'Donnell, and so on. The Senate Republican campaign committee is promising to try and weed out unelectable candidates early, but it's not clear they will be able to do so.

Each possible post-2014 outcome means different things for the 2015/2016 Senate — but also means different strategies for the Senate right now.

Scenario 1: The Democrats retain the majority.

Likelihood: high. Obama's nominees to sit on the D.C. Circuit Court of Appeals, the appeals court responsible for weighing in on a broad swath of federal legislation, have consistently been blocked by the Senate Republicans, using their ability to filibuster to force the need for a 60-vote supermajority before nominees can move forward. Last week, Massachusetts Sen. Elizabeth Warren lambasted Republicans, insisting that they were trying to nullify the 2012 election by not allowing the president to nominate his choices to the court.

The Senate Democrats have repeatedly threatened to revoke the right of the minority to filibuster appointees — but haven't done it, in part because of that nagging question of what happens when the power in the chamber flips. In its assessment of the likelihood of a rules change, Politico notes that this concern may be stronger with a "new generation of senators" — those who will serve in the Senate longer and are more likely to see the power balance flip.

If it becomes clear over the short term that the Democrats will retain control of the Senate, that the Republicans won't get the six vote margin they need to assume control of the chamber,Democratic leaders may feel more empowered to make the rules change. The Democrats would need to lose both the presidency and the Senate after 2016 in order for this to become a problem for the party — and even then the D.C. Circuit would need to see additional retirements in order for that Republican president to get the ability to make appointments.

Scenario 2: Republicans get a filibuster-proof majority.

Likelihood: Very low. If 2014 turns into a Republican landslide election, sweeping 25 new Republican senators into office, the significance goes far beyond procedural issues in the Senate. It would mean wins in races that Republicans currently trail by wide margins, meaning that the race itself is likely a repudiation of Democrats and the President. If this were to happen, Obamacare would certainly be at risk — as would a host of other legislation.

Scenario 3: Republicans get a majority.

Likelihood: Medium. The Republicans need a net gain of six senators in order to take control of the Senate. This doesn't mean much for the president's nominees — as Politico noted in its article this morning, the idea that the opposition party would only block extreme appointments has already gone out the window. If the Republicans take power in the Senate, it's not clear that the party would move any nominees forward beyond the most middle-of-the-road candidates.

But as National Journal points out, the threat of a Republican majority could affect the Obamacare debate.

But [Senate Majority Leader Harry] Reid and the White House may end up relying on swing-state Democrats like Claire McCaskill and Bob Casey to protect the law. If the political mood doesn't improve in short order, will they want to be in that position? And if Republicans retake the Senate in 2015, the political momentum for repeal would only grow.

In other words: If it looks like Republicans are gaining ground, will wavering Democrats want to stand strong on the bill? Last week, 39 Democrats defected on a House bill that would have weakened Obamacare — largely but not exclusively Democrats in iffy political positions. As the election nears, keeping Democrats in line on tough votes will only become harder.

(The value of a clear majority: The Senate won't take up that House bill.)

Scenario 4: The Senate is evenly split.

Likelihood: medium. There is the unhappy possibility that the 2015 Senate could have 48 Democrats, two independents that join the Democrats on votes, and 50 Republicans. At that point, Vice President Biden gets to cast tie-breaking votes on contentious issues. There's only one clear winner here: The American public, that would get to see a lot more of Joe Biden.