Since taking office, Barack Obama has run the table on congressional Republicans, racking up one government-expanding victory after another — from the stimulus to Dodd-Frank, Obamacare and the $620 billion in fiscal-cliff tax increases.

The GOP’s sole victory — its one, lonely government-reducing achievement — was the passage of the Budget Control Act in 2011.

Now, House Republicans are retroactively conceding that fight, too.

Thanks to the Budget Control Act, the status quo for the first time favors fiscal responsibility. If Congress does nothing, government spending is set to go down automatically next year. For years, the default position in Washington has been to increase spending; now the default is to reduce it.

So why are Republicans agreeing to reverse their only fiscal victory of the Obama era? Simple.

The GOP has PTSD.

Republicans emerged from their last budget battle with a bad case of post-traumatic stress disorder. Scarred by the government shutdown, they are terrified of having another fiscal fight with the president in January. So they are unilaterally conceding before it even begins.

This is partially understandable. The government shutdown was a disaster for Republicans. And it is true that many of the conservative groups now opposing the Ryan-Murray budget deal are the same ones who forced the GOP into that suicidal fight, only to later admit it was unwinnable from the start.

But the lesson of the shutdown debacle is not that Republicans should not fight; it is that they should not fight stupid.

Big difference.

Trying to defund Obamacare was a losing battle; standing behind the Budget Control Act is a winning one. During the shutdown, Republicans were trying to force Obama and the Democrats to change current law. Here, they would be saying: Let’s not change current law at all. These are the spending cuts both sides agreed to. So let’s keep the government running at current levels, with no changes (including to Obamacare funding), and let the second round of sequester spending cuts take effect — cuts Democrats agreed to — automatically reducing spending to $967 billion next year.

Are Democrats really going to shut down the government in January to bust spending caps they voted for and Obama signed into law? Of course not.

If they tried, all the arguments they used in the shutdown fight would be turned against them. Back then, Democrats accused Republicans of refusing to accept current law — Obamacare. Now Democrats would be refusing to accept current law — the Budget Control Act. How could they shut down the government over a law they voted for? That would be nonsensical.

To win a fight over Obamacare, Republicans had to force Democrats to undo their signature achievement. To win the fight over the Budget Control Act, Republicans don’t have to do anything. They simply have to defend the status quo. They need to sustain current law.

Instead, House Republicans agreed to a deal that would reverse the automatic cuts in the Budget Control Act and raise spending by $63 billion over the next two years. Worse, the deal pays for half of that new spending by raising new revenue. So under this deal we’re raising spending, raising revenue and growing government. How is that conservative?

Half of the replacement cuts are scheduled to occur in 2022 and 2023, after the Budget Control Act expires. So we are trading certain cuts today for uncertain cuts a decade from now. What is to stop Congress from undoing those cuts down the road? Lawmakers just reached an agreement to bust the bipartisan sequester spending caps. Who is to say they won’t undo these replacement cuts in the next 10 years?

The irony is that while the tea party-driven House passed the Ryan budget by an overwhelming, bipartisan 332 to 94 vote, it may be the establishment-controlled Senate that kills the deal. Rep. Paul Ryan’s Senate counterpart, Budget Committee ranking member Jeff Sessions (Ala.), announced that he would filibuster the bill, which means it will require 60 votes to pass. So far, the only Senate Republican who has come out in favor of the deal is John McCain. Those openly opposing it include the top four GOP leaders — Mitch McConnell (Ky.), John Cornyn (Tex.), John Thune (S.D.) and John Barrasso (Wyo.) — as well as Republican Sens. Bob Corker (Tenn.), Lindsey Graham (S.C.) and Kelly Ayotte (N.H.).

In other words, this is not a Ted Cruz-driven suicide mission.

Senate Republicans should kill this deal and then insist that Democrats stick to the spending levels they agreed to in the Budget Control Act. If the Democrats want to shut down the government because Republicans won’t increase spending, let them try.

That is a fight worth having — and one Republicans can win.

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