Harry Reid’s decision to pull the trigger on the “nuclear option” in the fall may end up producing some unexpected fallout for Democrats next fall: the loss of their Senate majority.

Reid sowed the seeds of his own destruction by changing the calculus in the 2014 midterm elections. Before Reid went nuclear, tea party challengers and their supporters (this columnist included) could correctly argue that winning the majority really did not matter. Since the GOP needed 60 votes to overcome a Democratic filibuster — something that was clearly out of reach — why not gamble and challenge the establishment? The GOP had gone astray when it came to fiscal responsibility, and a Republican reformation was more important than a Republican restoration. To paraphrase former senator Jim DeMint, better to elect 30 true conservatives than compromise for a powerless moderate majority.

That rationale disappeared when Reid invoked the nuclear option. Now winning the majority really does matter.

While Reid’s nuclear strike was limited to executive-branch nominees and judges below the Supreme Court level, it set the precedent that the majority could change Senate rules when it suited them. If Republicans win control of the Senate this fall, there is nothing to stop them from invoking Reid’s example. And if Republicans win the presidency in 2016, the nuclear option could have far-reaching consequences.

Take Obamacare. Does anyone think for a moment that a Republican Senate majority is going to let a handful of Senate Democrats stop them from repealing Obamacare in order to protect the institutional rights of the minority? Of course not. If Republicans take back the Senate and the White House, they can follow the Democrats’ lead, change the rules and repeal Obamacare with just 51 votes. And for conservatives upset over the Supreme Court’s Obamacare ruling, Reid’s action will make it easier for a Republican president and Senate majority to transform the high court. If Republicans are not allowed to filibuster lifetime appointments to circuit courts, why should they let Democrats filibuster lifetime appointments to the Supreme Court?

Ultimately, Reid’s action strengthens the hand of establishment Republicans facing conservative primary challengers — because the fate of Obamacare now hangs in the balance. The government shutdown proved that without control of the Senate, the GOP will never be able to repeal Obamacare. Tea party voters now have a tougher choice to make. Before the nuclear option, they could cast their ballots for the most conservative candidate, regardless of electability. Now they need to ask themselves which is more important: ideological purity or winning the majority and repealing Obamacare?

The stakes are high because a GOP Senate majority is within reach. As the National Journal recently reported, “[T]he 7 seats most likely to switch parties [in 2014] ... are only Democratic-held. If Republicans flip 6 of the 7 — without losing any of their own vulnerable seats -- they would control the Senate in 2015.” Democrats are vulnerable because of the disastrous Obamacare rollout and the public’s anger over the president’s false promise that if you like your health plan and your doctor, you can keep them. There are 12 Senate Democrats on the ballot in 2014 who made that exact same promise. Some of them will pay the price.

None of this is to suggest that conservative primary challenges are a bad thing. To the contrary, they have produced outstanding conservative leaders, such as Sens. Pat Toomey (Penn.) and Marco Rubio (Fla.). And even when challengers don’t win, they keep establishment Republicans accountable to the grassroots. The effect of establishment Republicans getting knocked off in the last two election cycles has made the Senate more conservative — because Senate Republicans vote differently when they are worried about a primary than they would have if they thought they could cruise to reelection. We get two good years out of them, thanks to the tea party. Moreover, it is a myth that nominating establishment candidates is the key to victory. If that were so, Tommy Thompson would be in the Senate today.

But before Reid pulled the nuclear trigger, the primary goal for grassroots conservatives was to reform the GOP. That meant it was worth losing Delaware’s Senate seat to prevent the election of a Republican squish like Rep. Mike Castle. Now tea party conservatives have to balance the objective of Republican reformation against another one that is just as important: repealing Obamacare.

Thanks to Reid, establishment candidates have an argument in 2014 they did not have in the last two election cycles:

The majority matters.

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