MINNEAPOLIS — Gov. Mark Dayton holds a strong lead over Republican Jeff Johnson in his bid for a second term, but plenty of voters haven’t made up their minds yet, according to a statewide poll published Sunday.

The poll for the Minneapolis Star Tribune has Dayton at 45 percent and Johnson at 33 percent, with a sampling error margin of plus or minus 3.5 points. Twenty percent of those surveyed hadn’t yet made up their minds.

The poll also found a big gap in name recognition, with Dayton — a longtime political figure in the state — at 100 percent and Johnson unknown to at least a third of respondents.

Johnson said he knew going into the race that he’d have to raise his name recognition. But he also said the number of undecideds give him a plausible path to victory.

“The key for me is to continue to campaign and to get ads up on television, which we will soon,” Johnson said. “Once I start sharing my vision, I would hope it starts to heavily break my way.”

Neither campaign has launched their own TV ads yet, but Alliance for a Better Minnesota, a liberal group that supports Dayton, has aired several ads criticizing Johnson. The Democratic-Farmer-Labor Party is launching a $1 million TV ad campaign for Dayton this week.

Johnson said his campaign would be on the air by the end of September.

Dayton campaign spokeswoman Katharine Tinucci welcomed the poll’s assessment of the size of the governor’s lead. One number of possible concern for Democrats: an approval rating of 46 percent, down from 58 percent in a February poll for the newspaper.

The poll of 800 likely voters was conducted Sept. 8-10 on land lines and cell phones.