It's becoming a tradition for winning gubernatorial candidates to make campaign promises to preserve 400,000 acres from development.

Tim Kaine did it in 2005 and state figures show he met his pledge. Bob McDonnell followed suit in 2009, but was only able to protect slightly more than half of the promised acreage. Undaunted, Terry McAuliffe issued the same vow during his 2013 campaign.

"I pledge to preserve at least 400,000 acres of open space over the next four years," McAuliffe said in an Oct. 30, 2013, op-ed in Politico.

McAuliffe, who took office in January 2014, reiterated his goal during his maiden speech to the General Assembly. "By the end of my term, I hope to stand here and announce that we have secured an additional 400,000 acres for the enjoyment of many Virginia generations to come," he said.

But one-third of the way into his term, McAuliffe is progressing at even a slower pace than McDonnell during his unsuccessful bid to reach the conservation goal.

Virginia has preserved about 36,500 acres under McAuliffe, according to Molly Ward, the secretary of natural resources. She told us economic uncertainties have undercut a major conservation incentive -- Virginia's Land Preservation Tax Credit. The program in recent years has provided up to $100 million annually in tax credits to landowners who donate their property, or give the state an easement to it, for conservation. The tax break amounts to 40 percent of the appraised value of the land.

Ward said a large problem -- also cited during McDonnell's administration -- is that land prices have not recovered from the Great Recession. That makes the prospect of donating land for tax breaks less attractive and requests for the credit have been coming in lower than the $100 million cap. During fiscal 2014, property owners claimed only $70.6 million in land preservation tax credits.

This year, McAuliffe signed legislation lowering the annual pool for the credit to $75 million. What's more, the most any landowner can individually claim each year was dropped from $100,000 to $20,000 in 2015 and 2016. That will increase to $50,000 in 2017. The changes were among many budget-trimming measures approved by the General Assembly.

McAuliffe also is shifting gears to emphasize what the administration says is "quality rather than just quantity" in land conservation. On Earth Day this year, he announced a "Virginia Treasures" initiative that will focus on protecting parcels that may be small in acreage, but significant in other ways, such as protecting water quality and improving public access to pristine parcels. The program aims to protect 1,0000 "treasures" -- which could include trails, wetlands, as well as agricultural and forest parcels.

Despite the changes, Ward said the administration hasn't abandoned its original conservation pledge. "We certainly want to preserve as large a number (of acres) as we can. We would love to preserve 400,000 acres," she said.

But it always was going to be tough for McAuliffe to deliver on this pledge, and changes he's backed to narrow the land preservation tax credit make the odds even longer. We'll keep you posted. For now, we rate his promise "Stalled."