Either they'll raise $13 million in five months or they've embarked on a mission impossible. But the co-chairs of the Montana History Center Museum Campaign Committee sounded upbeat Monday when they announced that the effort has formally begun.

And, although they obviously would like to find donors with especially deep pockets, former First Lady Betty Babcock and former state Attorney General Joe Mazurek stressed that they're looking for donations of all sizes: "We are asking all Montanans to join us. This fundraising campaign is short and sweet -- we need your help now."

The museum project was sparked by news that the Capital Hill Mall between Prospect and 11th avenues may be for sale, leading to dreams of a world-class historical museum on the 13-acre site. Subsequently, Gov. Brian Schweitzer negotiated a $6.5 million purchase price for the mall, well below its estimated $10 million-plus appraised value. But he said that if supporters can't raise the $13 million in donations by Nov. 15, the whole deal is off.

The back-up plan is a less ambitious building on a parking lot just north of the current museum -- a plan that actually was preferred by Historical Society officials who questioned the feasibility and the expense of the mall-site proposal.

But backers of the mall site insisted that the museum's vast collections deserve a fully adequate facility, only possible on such large acreage. And, of course, they contend that the highly visible, highly accessible mall site is ideal.

We've said all along that -- long shot or not -- the chance to build a truly top-notch museum is worth going for. Now, over the next five months, we'll learn whether such a lofty goal can be reached.