Who woulda thought that President Barack Obama would take a PR cue from former President George W. Bush? At least on one key measure, he will — promising at a budget summit Monday to “cut in half” the $1.3 trillion deficit that he inherited by the end of his first term.

[IMGCAP(1)]That’s a neat trick, given that Obama’s reported deficit projection in four years is a whopping $533 billion, which itself would be a record if it weren’t for the current year’s ocean of red ink.

In 2004, while running for re-election, Bush proposed cutting the budget deficit “in half” by 2009. But that was only after a large surplus morphed into a large deficit during his first term. Bush technically succeeded in reaching his goal — and even projected a return to budget surpluses — before the bottom dropped out of the economy on his way out the door.

Which is why one might want to take any of these budget projections with, say, a trillion-dollar grain of salt, or two.

Congressional Democrats who made a living whipping out charts of skyrocketing federal debt will have to figure out a way to put a shine on an Obama budget that will explode the federal debt faster than any other president in the nation’s history. And those old charts could quickly become props for a smaller, feistier Republican minority hoping to regain the mantle of fiscal responsibility.

Bush, of course, blamed the 9/11 attacks, among other things, for the budget bloat that he amassed, but Democrats pointed to his unprecedented juxtaposition of tax cuts and wars.

Obama, for his part, can point to the enormous deficit that he inherited from Bush and set himself a low bar to jump over.

In the meantime, amid several trillion in additional borrowing, Obama and the Democrats plan to talk a lot about fiscal responsibility in the coming months.

Obama told top House and Senate leaders at the White House on Monday that he is committed to a range of new budget rules to improve transparency and promote action on long-term fiscal challenges.

“I refuse to leave our children with a debt that they cannot repay, and that means taking responsibility right now in this administration for getting our spending under control,” Obama said. “We’ll start by being honest with ourselves about the magnitude of our deficits. For too long, our budget process in Washington has been an exercise in deception, a series of accounting tricks to hide the extent of our spending and the shortfalls in our revenue and hope that the American people won’t notice.”

The new president said he will budget for wars, natural disasters and other costs that were previously left out of budgets to present a rosier picture.

Obama also has pledged to fully restore the old Democratic standby of pay-as-you-go budget rules — finding offsets elsewhere to accommodate spending increases — which have been cast aside of late by stimulus packages, tax cuts and new entitlement programs like the GI bill.

That promise of less fuzzy math and a return to PAYGO already has fiscally conservative Blue Dog Democrats singing Obama’s praises, despite the growing debt.

“This week alone, President Obama is doing more to address the serious long-term fiscal problems facing our country than former President Bush and his Congressional allies did during his entire eight-year tenure in office,” said Rep. Charlie Melancon (D-La.), a co-chairman of the Blue Dogs.

“We’re going to do honest budgeting,” said a Blue Dog senior aide, who brushed off the talk of trillion-dollar deficits. “To do that, your numbers are going to look bad on the front end.”

But far more difficult for Obama will be getting Congress to help him address some of the long-term challenges facing Social Security, Medicare and Medicaid, an effort that he kicked off Monday by inviting top lawmakers from both parties for the unusual budget summit at the White House.

Social Security, health care and tax reform were among the work sessions held between Members and the administration at the event, and Obama repeatedly reached out to senior Republicans, including his former rival for the presidency, Sen. John McCain (R-Ariz.), and said he would continue to do so.

Bush, of course, spent much of his second term calling for reform of Social Security, but his efforts fell short in the face of a massive partisan backlash.

But the Blue Dog aide said if Obama follows through on dealing with long-term fiscal challenges, it will go a long way toward easing the heartburn many of the fiscally conservative Democrats feel over voting for the $787 billion stimulus package.

“We’re in a deep hole, and it’s going to take all of us to get out,” the aide said.

Republicans thanked Obama for Monday’s invitations and urged him to get Speaker Nancy Pelosi (D-Calif.) to include them in writing legislation.

And Sen. Chuck Grassley (R-Iowa), ranking member on the Finance Committee, noted that the fiscal responsibility summit came after passage of a stimulus package that will expand the deficit.

“American taxpayers are being asked to swallow a lot right now, and it brings to mind the old joke about Wimpy’s hamburgers. Wimpy said, ‘I’ll gladly pay you Tuesday for a hamburger today.’ There’s too much of that kind of attitude in Congress and the White House today,” he said.

House Republican leaders, meanwhile, called Monday for a freeze on federal government spending, citing soaring deficits, and attacked the looming budget over its expected tax increases on the wealthy. And they trained their fire on the $410 billion omnibus spending bill that Democrats unveiled Monday, which will bolster spending on energy, health care and education significantly for the remainder of the fiscal year. Most federal agencies have been operating under a stopgap spending bill for nearly five months.

The GOP ripped Democrats for unveiling the bill just days before a floor vote.

“Democratic Congressional leaders should abandon their plans to rush another giant spending increase through Congress without public scrutiny and instead pass a clean bill that freezes spending at current levels,” House Minority Leader John Boehner (R-Ohio) said.

The bill could be voted on as early as Wednesday.