This week in the election campaign B.C. Liberal leader Christy Clark promised to cap tolls on the Port Mann and Golden Ears bridges at $500 a year.

A few hours later, NDP Leader John Horgan stepped up with his own promise to eliminate tolls on the two Lower Mainland bridges altogether, if elected on May 9.

It's The One Thing that made headlines this week on the campaign trail.

The One Thing is a CBC original podcast that looks at the one big issue that dominated the election campaign this week in B.C. It's hosted by CBC legislative reporter Richard Zussman.

In episode one, Zussman talks about the prominent role tolls have played in B.C. elections, past and present.

Listen to episode one of The One Thing here: