Pa. has far more undecided voters in the presidential race than most people thought, according to the latest poll from the Siena College Research Institute. President Obama leads Mitt Romney by 3 points with a whopping 17 percent of voters not aligned with either candidate.

That’s more undecideds than any Pa. poll has shown in the past month. 3 percent said they’re voting for someone else, and 12 percent said they haven’t made up their minds.

Siena surveyed 545 likely Pa. voters from Oct. 1-5 via landlines and cell phones.The margin of error is plus or minus 4.2 percent. The pollster says data has been statistically adjusted to reflect party registration, gender and age.

“With a month and two more debates to go, Pennsylvania’s direction on the road to the White House remains in doubt.  The final tally depends upon the sizable group of voters that in early October had yet to decide.  With clear differences in the Presidential race by party and area, turnout will make the difference,” said SRI’s Director Don Levy.

Why so many more undecideds than other polls? Levy said it’s because most pollsters ask respondents who say they’re undecided which way they’re leaning, then includes that number in the topline.

Because the race has grown more fluid since the debate, Levy said, he decided not to ask or include the followup “leaner” question. He said that based on what he’s seen, the increased in undecideds comes from people who had been tepidly backing Obama, but now consider themselves in the middle post-debate.

Obama is viewed favorably by 49 percent and unfavorably by 44 percent. Romney’s numbers are reversed: 49 percent unfavorable, 40 percent favorable.

Among voters who are independent, third parties or have no affiliation, Romney leads 31 percent to 30.

In line with other polling, Romney has a slight lead among men (44 percent to 43), while Obama has a wider advantage among women (44 percent to 36).

Most interesting are the pollster’s regional crosstabs, which show Romney dominating in the suburban southeast Pa. counties 49 percent to 35. Obama easily carried these areas in 2008. See update below.

Here’s the full regional breakdown:
Philadelphia: Obama 63, Romney 13
West: Obama 49, Romney 38
Northeast: Obama 48, Romney 27
Southeast: Obama 35, Romney 49
Central: Obama 33, Romney 51

Update: we talked with SRI, and found that their regional breakdown of Pa. is significantly different than other pollsters. Case in point: heavy GOP population centers like Lancaster and York counties are included in the “Southeast.” Here’s a map of Siena’s regions: