Should we worry about big government? For far too many Americans, the answer is “not when my team’s in charge!”

Since 2003, Gallup has periodically asked Americans whether the federal government “poses an immediate threat to the rights and freedoms of ordinary citizens.” The latest results are in, and in just four years Republicans’ and Democrats’ answers “have shifted dramatically.”

In September 2006, 57 percent of Democrats said yes, while only 21 percent of Republicans agreed. Since then, Congress and the White House have gone from red to blue, and the two camps have switched places. “What, me worry?” say all but 21 percent of the Ds today, while 66 percent of the Rs are ready to start provisioning their concrete bunkers.

For those of us who genuinely believe in limited government, Gallup’s results are depressing, if not surprising. Mindless partisanship remains a major obstacle to restoring constitutional limits on federal power.

Gallup tries to downplay political tribalism as an explanation for the results. After all, they write, Republicans worry more about “government involvement in health care,” while Democrats worry more about “wars or anti-terrorism activities.”

If voters’ threat perceptions are based “not on how much [government] is doing but rather on what it is doing,” then maybe both Rs and Ds had good reason to change their answers.

Nice try, but during the relevant period government was doing all of the above. In 2003, President George W. Bush pushed through a massive expansion of socialized medicine with Medicare Part D, whose price tag — $1.1 trillion over the next decade — dwarfs most estimates of Obamacare’s projected costs.

For his part, Nobel Peace Prize winner Barack Obama nearly tripled deployments to Afghanistan, and he’s lately claimed the power to kill American citizens with drone strikes. Both presidents relentlessly expanded federal power at home and abroad.

Alas, political tribalism warps people’s perceptions of basic reality, convincing partisans they’re entitled to their own facts. That’s nothing new.

In a 1988 survey, over half of self-identified “strong Democrats” believed inflation had increased under President Reagan, when it had actually come down nearly 10 points. Half of the Republicans in a 1996 poll believed Bill Clinton had increased the deficit, though it dropped steadily during his tenure. Political scientist Adam J. Berinsky puts it starkly: “In the battle between facts and partisanship, partisanship always wins.”

In 2004, psychologist Drew Westen took a look at the partisan mind through an MRI scanner. He presented 15 “strong Democrats” and 15 “strong Republicans” with negative statements about their favored candidates and watched which parts of their brains lit up.

“None of the circuits involved in conscious reasoning were particularly engaged,” Dr. Westen reported — it appeared “as if partisans twirl the cognitive kaleidoscope until they get the conclusions they want.”

It could be that mindless partisanship, like original sin, is in our genes. The tendency toward irrational group loyalties may have gotten hardwired in because it served us well during the long period man developed as a hunter-gatherer living in small tribes.

Maybe so, but we’re supposed to be the ape that reasons. The threat presented by big government hardly turns on whether the federal juggernaut’s currently painted red or blue. Even if you’re convinced one tribe is far worse than the other, it doesn’t take a genius to recognize that political power regularly changes hands.

The Tea Partiers, slow to awaken during the Bush years, now appear genuinely passionate about shrinking government. Let’s hope they maintain that passion, whatever November brings.

“Eternal vigilance is the price of liberty” runs the adage. “Eternal” means even — perhaps especially — when the faction you favor is at the helm.