Even the lure of millions for BART wasn't enough to convince Livermore-area voters to approve an Alameda County transportation sales tax in November.

It narrowly lost the election in part because it failed by large margins in Livermore and Pleasanton despite $400 million set aside for an extension of BART to Livermore.

Although the measure won big votes in Berkeley, Oakland and Emeryville, some 52 percent of Livermore and Pleasanton voters rejected Measure B1, leaving the tax hike just shy of reaching the countywide threshold of 66.67 percent needed to pass.

Transportation leaders say understanding the lackluster support in the Tri-Valley may be key to crafting another tax hike to take to voters -- perhaps in 2014.

Measure B1 received 66.53 percent support countywide -- failing to pass by about 700 votes. The measure would have doubled the county transportation sales tax to a full one cent, raising $7.8 billion over 30 years to boost spending for roads, freeways, public transit, trails and bike lanes.

The current half-cent tax expires in 2022.

In sharp contrast to its Tri-Valley reception, the tax hike was backed by 80.8 percent of voters in Berkeley, 76.3 percent in Oakland and 77.56 percent in Emeryville, according to Alameda County Transportation Commission figures.

The measure got two-thirds support in five cities and fell short in nine.

Pleasanton and Livermore were the only two that failed to give at least 50 percent support.

The measure did a little better in Dublin, getting 54.6 percent support.

Several county transportation leaders said they were surprised the measure did so poorly in the Tri-Valley despite the $400 million down payment on a BART rail extension from the Dublin-Pleasanton station to Livermore.

"I was stunned," Livermore Mayor John Marchand said of the tally in his city. "The measure provided something like $5,000 per every man, woman and child in Livermore just for the BART extension."

Marchand -- as well as Dublin Mayor Tim Sbranti, Pleasanton Mayor Jerry Thorne and County Supervisor Scott Haggerty -- agreed B1 lost Tri-Valley support because voters didn't want a permanent tax.

Past county transportation sales tax measures were limited to set periods unless renewed by voters.

"Everyone who told me they voted against it said it was because the tax was for perpetuity," said Haggerty, a Dublin resident and strong B1 backer. "The perpetuity scared people."

During the campaign, the Alameda County Transportation Commission said a permanent tax was essential to keep roads and public transit systems in good shape amid decreased state and federal funding.

Opponents said making the tax permanent was arrogant and doesn't make politicians accountable.

Sbranti, the Dublin mayor, said a permanent tax clashed with the Tri-Valley's more fiscally cautious views.

The three mayors and Haggerty said they favor putting a similar, nonpermanent tax before voters.

Greg Harper, an AC Transit board member from Emeryville, said northern and central Alameda County have traditionally supported transportation taxes in part because they have more public transit than in eastern Alameda County.

"People want to protect their service," he said.

Marchand, the Livermore mayor, said he thinks Measure B1 was hurt in his town by voter confusion about whether the proposed BART extension would be built along Interstate 580 or through downtown, a route that has drawn strong opposition.

The Livermore City Council initially backed a downtown route. In response to public outcry, the council switched to endorse a freeway route.

"I still talk to people who think BART is going downtown," Marchand said.

Marchand and Haggerty said they were disappointed the B1 campaign didn't do more to persuade Tri-Valley voters the tax would improve local freeways, roads, buses, BART and paratransit systems that carry seniors and the disabled.

"It was a disappointing to come so close and yet lose," said Haggerty, who is next in line to head the county transportation commission. "We need to get up, dust ourselves off and figure out how to come back with a plan that can win."

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.