The Conservative vote in Tuesday’s election may be three or four percentage points higher than polls indicate, pollster Angus McAllister says.

That’s because national polls may be missing parts of important demographic groups, McAllister said.

McAllister, of McAllister Opinion Research, said it appears that people who refuse to tell pollsters who they are going to vote for tend to be Conservative supporters.

Women aged 55 and over are twice as likely as other groups to refuse to tell pollsters who they’re going to vote for, McAllister said.

What’s more, women who won’t state a party preference tend to live in rural areas or in areas like the 905 belt outside Toronto.

And older women in these areas are twice as likely to vote Conservative than other demographic groups, McAllister said.

People who refuse to state a party preference tend to say that health and the economy are their top issues, he said.

“They don’t care about the environment. It’s all about health and the economy.”

He said the reluctance of Conservative supporters to talk to pollsters fits with social values research that indicates that older small-c conservatives tend to be less trusting than most people – and therefore less likely to tell a stranger on the phone who they’re going to vote for.

“It’s a theory,” McAllister said. “It’s not proven.”

But it is clear that who you get to answer your poll determines your outcome.

For example, McAllister said, American pollsters know that if you do a poll on a Friday night you’re likely to overstate Republican support. Democrats are more likely to go out at night than Republicans.

To offset such problems, pollsters can call refusers back repeatedly until they get an answer. But this isn’t possible with the quick-turnaround polls that have dominated this campaign.

“Polls that are overnight polls, three-day, two-day polls, polls that are really quick, there’s no way a pollster can make that amount of effort unless they have huge resources, which they usually don’t,” McAllister said.

People who refuse to state a party preference are different from those who say they don’t know who they’re going to vote for, McAllister said. “Don’t Knows” tend to lean toward the opposition parties in roughly equal numbers, he said.

McAllister said it’s also possible that the missing older women are balanced by a lack of young people, who tend to vote for parties other than the Conservatives.

Young people are “harder to get a hold of,” McAllister said. “They’re more mobile. They travel more, they’re home less often, they’re also on mobile phones. So we have to work harder to get young people.”

This might not have as much impact on election day, however, because young people are also much less likely to vote.

And one last thing to watch for: the Green party vote might fall short of the party’s poll standings, and not just because the Greens don’t have a big machine to get the vote out.

Many Green supporters, McAllister said, are telling pollsters they will “probably” vote.

“People who say they are probably going to vote don’t vote.”

Tom Barrett is a contributing editor at The Tyee.