Two polls that supply evidence that Herman Cain is not only a viable Republican candidate, but can challenge Obama in a general election contest.

Poll position:

In a hypothetical head-to-head presidential race, Republican Herman Cain edges Democrat Barack Obama, according to our latest national scientific opinion poll.

The poll found Cain topping Obama by a narrow 43%-41% margin, with 15% saying they had no opinion. The 2% difference falls within the poll's 3% margin of error.

Poll Position's scientific telephone survey of 1,135 registered voters nationwide was conducted October 9, 2011 and has a margin of error of ±3%.

And Gallup has Romney and Cain neck and neck:

Republicans' support for Herman Cain has surged to 18%, their support for Rick Perry has sagged to 15%, and their support for Mitt Romney remains relatively stable at 20%. However, Romney's support is matched by the 20% of Republicans who are unsure which candidate they will back for the Republican nomination in 2012.

Gallup's Oct. 3-7 update of Republicans' preferences for their party's 2012 presidential nominee shows that Romney since mid-September has regained a numerical lead over the rest of the field, mainly because Perry's support has dropped by half over the same period. At the same time, support for Cain has more than tripled, from 5% to 18%, creating a competitive three-way race for the nomination between Romney, Cain, and Perry -- all within five percentage points of each other. Prior to now, Gallup has had Romney out front, Perry out front, or a two-way battle between them.

Also of note in the new results are Ron Paul's return to single-digit support levels, and the failure of Michele Bachmann, Newt Gingrich, Rick Santorum, and Jon Huntsman to make significant gains.

The GOP debate tonight will have Cain in the crosshairs for the first time. It will be interesting to see how he handles the pressure. My guess is he'll do fine, deflecting tough questions with his characteristic humor. But it's hard to gauge how anyone will perform with that kind of pressure.