Members of Congress meeting constituents in their district this week are likely to encounter an unusual dynamic: Obamacare supporters who suddenly seem to outnumber the law’s opponents.

The New York Times’s Jonathan Martin wrote this weekend about a new reality dawning on congressional Republicans: Constituents who dislike Obamacare are no longer anywhere near as vocal as they used to be, while the health law’s supporters are suddenly more energized than ever.

Many have remarked on how this seems to be a mirror image of 2009, when the Tea Party became far more mobilized in opposition to Democrats’ health reform legislation than supporters were. And it’s also, of course, worth remembering that Democrats forged onward with health reform regardless of these prominent protests.

But there’s also a crucially important difference between the two situations: The 2009 Democratic proposal planned to give out new benefits, while GOP proposals for Obamacare repeal today would instead put existing benefits at risk. In practice, the politics of those respective scenarios have tended to play out very differently. Yes, a new law giving people stuff — in the form of either new benefits or tax cuts — can be controversial and difficult to pass.

Messing with the stuff people are already getting has tended to be exponentially more controversial, though, because it’s more actively harmful. Simply put, politicians of all stripes are more eager to go out on a limb to help their voters rather than to support something they believe will harm them.

Remember the fate of Bush’s Social Security plan

For a reminder of how this has worked, just think back to the last time Republicans had control of both the White House and Congress — from 2003 to 2006, under George W. Bush.

Though GOP rhetoric has often focused on the need to cut spending, Bush had his greatest domestic legislative successes in his first term, when he focused on giving people stuff. Namely, he enacted two big rounds of tax cuts and the Medicare Part D prescription drug benefit. None of those victories came easy — Republicans were forced to scale back their second round of tax cuts, and the final House vote on Medicare in 2003 was famously controversial. Still, all of them ended up passing in the end.

But fresh off his reelection to a second term, Bush decided to make a bold proposal to overhaul the existing Social Security program by partially privatizing it. This did not end well for him.

I recapped this story at greater length in an article back in January. Overall, though the defeat of Social Security reform had many elements — administration missteps, a unified Democratic opposition, and so on — the most important one is that the proposal, at its core, was about messing with the benefits people were already getting.

Politicians looked for feedback from their constituents on Bush’s plan, and what they heard was so negative that even moderate red-state Democrats temperamentally inclined toward bipartisanship, like then-Sen. Max Baucus of Montana, decided the plan was a loser. By early February, New York Times reporter Robin Toner could report on “a general anxiety attack in the Republican center over Social Security.” Eventually, all the major players became convinced it couldn’t pass, and the centerpiece of Bush’s second-term domestic agenda was never even brought to a vote.

Obamacare’s situation now isn’t a perfect parallel here. It’s a much younger program than Social Security, and there’s a stronger case that the exchanges may be in some trouble and in need of an imminent overhaul.

Plus, Obamacare repeal has been the centerpiece of Republican messaging for years, whereas Social Security privatization was never more than a minor issue during the 2000 and 2004 campaigns. Still, as Martin’s story suggests, this GOP base enthusiasm may have ebbed, and it’s worth keeping the fate of Social Security reform in mind.

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