Many Republican candidates are pinning their hopes for victory in this year's congressional elections on the public's justified concerns about the misnamed Patient Protection and Affordable Care Act.

Make that too many Republican candidates.

Meanwhile, a growing number of Democrats are boasting that an unexpectedly high number of Americans have signed up for insurance under the law - and citing that statistic as a sure sign that it's working.

But that's a dubious argument - and some of their party colleagues are still running away from Obamacare.

Beyond expectations of Obamacare's side-effects on November's political outcome, however, lies a defining bipartisan test for our nation.

Though conservatives make a strong case that the Affordable Care Act is not good for what ails America's economy, that law is merely a huge symptom of unaffordable Nanny State excess, not the disease itself.

And for the GOP to credibly present itself as the party of fiscal responsibility, its candidates must do more than oppose Obamacare. They must propose hard choices needed to save our nation from fiscal disaster.

Anyway, no Republican so far can match the president in blocking the mandates of that landmark legislation, which he signed four years ago after it passed without a single GOP vote.

And many Americans now understandably suspect that changes in how the Census Bureau counts who is and isn't insured mask Obamacare's consequences.

As Sen. Lamar Alexander, R-Tenn., put it last week: "After unilaterally decreeing 22 changes to the health-care law, the administration may now have found a way to alter the basic facts."

But here's another basic fact: Some prominent GOP senators, including 2016 White House hopefuls Rand Paul of Kentucky and Ted Cruz of Texas, refuse to back the bold budget recently passed by the GOP House - or to propose specific spending plans of their own.

Republicans long and fairly decried the Democratic Senate's failure to pass a budget in 2010, 2011 and 2012, until it finally did so last year, as an appalling neglect of legislative duty.

That doesn't mean the House spending plan, crafted in large part by Budget Chairman Paul Ryan, R-Wis., is perfect. But it would cut more than $5 trillion in federal spending over the next decade en route to - at least on paper projections - budgetary balance.

In contrast, the president's budget plan would produce a net 10-year deficit reduction of a mere $158 billion.

The House spending bill, heavy on cuts in social programs, passed the House by a slim 219-205 margin on April 10 - without a single Democratic vote and with 12 Republicans voting against it.

Of course, just as the president's plan has no chance of passing in the GOP House, the House plan has no chance of passing in the Democratic Senate.

And our nation's future fiscal viability has no chance if our elected officials keep postponing the tough calls required on not just Obamacare but Medicare, Medicaid and Social Security.

As for that House budget, Rep. Ryan pointed out:

"Some people wanted to go further, some people thought it went too far. The point is we unified around these common principles in a plan. That's very important to me - which is we can't just oppose, we have to propose."

And Americans, regardless of political persuasion, should demand that elected officials in Washington agree on "common principles" to determine what the federal government, i.e., federal taxpayers, can - and can't - afford.

That high-stakes, bottom-line challenge will persist long after this year's elections.

And the only way to meet that challenge is to solve the problem of unsustainable federal programs - not just Obamacare.