The new Quinnipiac poll’s findings on public attitudes on the crucial upcoming debt limit fight ought to give serious pause to Republicans. They thought voters were on their side, but the latest evidence shows they aren’t.

The GOP and its outside supporters were emboldened on Sept. 26 by a Bloomberg poll showing that by 61 percent to 28 percent, voters said it would be “right to require spending cuts when the debt ceiling is raised, even if it risks default” on the government’s debts.

It was seen as a repudiation of President Barack Obama’s stance that bills previously contracted by the government had to be paid and that he would not negotiate about it.

Republicans thereupon decided they could load nearly their entire agenda onto the debt vote, including delay or repeal of Obamacare, fast-track authority for tax reform, a rollback of EPA regulations on greenhouse gases and coal ash emissions, medical malpractice caps and restrictions on the new Consumer Financial Protection Bureau.

They also took encouragement from an NBC/Wall Street Journal poll showing that the public, by 44 percent to 22 percent, opposed raising the debt limit.

And any number of polls, of course, have shown a decline in Obama’s approval ratings.

The Quinnipiac poll out Tuesday also shows Obama’s approval somewhat under water — 45 percent positive, 49 percent negative.

But the results were devastatingly negative on GOP tactics on both the government shutdown and the debt limit. By 77 percent to 22 percent, the public opposed the GOP tactic of shutting down the government to block implementation of Obamacare.

And by 64 percent to 27 percent, voters opposed blocking an increase in the debt ceiling to stop Obamacare.

They are split on Obamacare — 45 percent pro, 47 percent anti — but they opposed cutting off its funding 58 percent to 34 percent.

Undoubtedly hardliners on the Republican side — maybe leaders, too — will say, forget Quinnipiac and believe Bloomberg.

But there’s other evidence that the public understands that not raising the debt ceiling and not being able to pay the government’s bills is a bad idea.

The Washington Post/ABC poll on Sept. 18 showed that by 73 percent to 22 percent, voters believe that not raising the limit would cause “serious harm” to the economy. It’s true that voters favored raising the limit by only 46 percent to 43 percent. But, on the question of which side — Obama or the Republicans — was doing too little to compromise with the other, it was 49 percent, Obama, and 64 percent, the Republicans.

The bottom line is that Republicans are risking both political and economic disaster if they persist in loading multiple conditions onto the debt limit vote later this month.

A government shutdown, if it doesn’t last too long, will cause pain, but not risk the fundamental health of the economy. Defaulting on the national debt well might — and the latest evidence is that the GOP will get (and deserve) the blame.