Some Virginia Democrats have looked at Barack Obama’s sliding popularity recently and backpedaled from the president. But not Tim Kaine.

He stood by his man in a scrappy U.S. Senate campaign debate Wednesday, repeatedly defending the president against criticisms by Republican George Allen.

Since Allen voiced pretty much the standard GOP list of Obama’s supposed failings, the verbal match offered a fine preview of the 2012 national debate over whether to reelect the president.

Almost from the start of the 90-minute duel at the state Capitol here, Allen sought to discredit Kaine by linking him to Obama. No surprise there. The GOP likes to portray Kaine as Obama’s “cheerleader in chief” for his time as chairman of the Democratic National Committee. The Republicans think it will be a winning formula, given that Obama’s approval ratings in the state have been well below 50 percent in some opinion surveys.

So it was a bit of a surprise — and frankly refreshing — to see Kaine defend the president’s record without hesitation. He didn’t go out of his way to bring up Obama. But he also didn’t waffle or try to distance himself from the president’s policies, polls be damned.

The $800 billion stimulus package that added to the federal debt and hasn’t appreciably reduced unemployment? Kaine said it succeeded in halting what was then an economic free fall.

The ultra-controversial national health-care bill? Kaine said it needs improvement, but he praised it for extending insurance to millions of Americans, including more than 1 million in Virginia.

Describing the long lines of needy patients who regularly show up for care at an annual charity-funded free clinic in Wise County, in southwestern Virginia, Kaine said, “We don’t need something like that in the richest nation on Earth.”

In one telling exchange, Allen accused Kaine of neglecting Virginia’s interests in his final year as governor, when he’d also taken on the job of DNC chairman. Allen, a former governor himself, said Kaine was advocating for “the likes of not only President Obama’s policies but those of Nancy Pelosi.”

Kaine interrupted at that point, shaking his head: “The likes of President Obama?” He seemed incredulous — or, more likely, wanted to appear so.

Allen pressed ahead: “The policies and agenda of President Obama, Nancy Pelosi and Harry Reid: Were you or were you not advocating for their agenda? And their agenda surely was not consistent with the best interests of Virginia.”

Kaine’s response: “Wiping out al-Qaeda? Stopping the Iraq war? Saving the auto industry? That’s not being consistent with Virginia’s interests? I just see it a different way than you, George.”

Kaine’s approach was markedly different from that of some Democratic candidates who put space between themselves and Obama in the fall state legislative campaigns. Top state Democrats urged the White House to alter the president’s schedule at one point to keep him out of some districts where races were close.

The Wednesday debate also offered a glimpse at what’s in store for the country as a whole in the coming year on another key issue: Who’s to blame for federal overspending.

Both Kaine and Allen tried to pin the profligacy label on the other’s party. Kaine said Allen was at fault for supporting tax cuts and overspending on wars and prescription drug benefits when he was in the Senate from 2001 to 2007. That will be the Democrats’ argument: that the overspending is a legacy of George W. Bush’s presidency, which Allen supported.

Allen contended instead that most of the federal debt has piled up since Obama took office. In the debate, he whipped out a chart featuring red ink bar graphs to prove his point. That will be the GOP argument.

I would have liked to have seen both candidates spend less time on assigning blame and more on spelling out what the country should do to get the economy moving again.

In this match, the public got only brief sound bites on that issue. Kaine said the country needs to “win the talent war” by investing in education, research and development, and immigration reform. Allen said the nation needs to “reinvigorate the entrepreneurial spirit” by avoiding tax increases, cutting spending and boosting energy production.

If such boilerplate can become real blueprints for encouraging long-term growth — while reducing the deficit over time — then we can have a full, substantive debate about the nation’s economic future.