Beware of polls… but this is promising.

Republican Gov. Scott Walker leads Democratic challenger Mary Burke 50% to 43% among likely voters in a new survey by the Marquette University Law School.

That represents a change from other surveys in recent weeks — including Marquette’s previous poll two weeks ago — showing the race essentially tied.

Marquette surveyed 1,164 likely voters from last Thursday through Sunday. The poll has margin of error of plus or minus 3 percentage points.

The race is much tighter among all registered voters — with Walker leading Burke 46% to 45%.

the shift toward Walker among the most likely voters in the poll reflects a spike in the share of Republicans who say they are certain to vote.

In Marquette’s last poll, 82% of Republicans and 80% of Democrats said they were certain to vote.

In the new poll, 93% of Republicans and 82% of Democrats said they were certain to vote. Those numbers, reflecting a potential turnout gap between the parties, are similar to what voters were reporting before the recall election of 2012, which Walker won by 7 points.