By Pat Kessler

MINNEAPOLIS (WCCO) — Minnesota’s turbulent 2018 midterm election is finally over, and it brought some surprises.

For many months, polls projected possible winners and losers. So how accurate were they?

Public opinion polls do not predict the future — they take a photograph of the present. But over time, polls can accurately demonstrate political trends.

DFL candidate for governor Tim Walz averaged a 10-point lead over Republican Jeff Johnson. Walz won by 12 points [54 percent to 42 percent].

Public polls had Democratic Sen. Amy Klobuchar up an average of 20 to 30 points over Republican Jim Newberger. She won by 24 points [60 percent to 36 percent].

Polls gave Tina Smith an eight-point edge. The Democratic Senator won by 11 points [53 percent to 42 percent].

Here is a 2018 race the pollsters got wrong. Summer polls had former Governor Tim Pawlenty up 14-points over his Republican rival Jeff Johnson – who ended up winning the primary by 8.5 points [53 percent to 44 percent].

With some exceptions, history shows polls are generally accurate, with margins of error. But polling methods are changing rapidly with technology.

Public polls used to be conducted by making telephone calls on land lines. Now, it is a combination of land line, online, and cellphones.

National polls predicted Hillary Clinton would win the popular vote by three percentage points, and she won by two points.

State polls missed the Trump surge in Wisconsin, Michigan and Pennsylvania

This year, the New York Times called 19,000 people for just one poll in Minnesota’s 8th District to scientifically sample 507 respondents. It put Republican Pete Stauber up 15 points.

Stauber won — by six points [51 percent to 45 percent].

Here are some of the sources we used for this Reality Check:

Minnesota Election Results

NYT List of Minn Polls

Real Clear Politics: Pawlenty-Johnson Primary

NYT: Midterm Election Forecast MN-8

New York Times Live Polling: MN-8

Real Clear Politics: Walz-Johnson

Real Clear Politics: Klobuchar-Newberger

Real Clear Politics: Pawlenty-Johnson

Scientific American: How Polls Work

How To Read Polls

Pat Kessler