BANGOR (AP) — Five of the six contestants for Maine’s open U.S. Senate seat met in a debate Wednesday night in the latest of several exchanges among the candidates, and while a lot of old issues were covered a few new barbs were hurled.

The debate got testy when two of the three front-runners in the race, former independent Gov. Angus King and Republican Secretary of State Charles Summers, were asked about campaign ads that have been virtually nonstop on Maine television since early in the campaign.

Summers drew a round of groans from the mostly silent audience of nearly 300 at Husson College when he said King “is the only one on the stage running negative ads.”

King, the assumed front-runner who has been hit by a barrage of independent ads, responded that that’s “like being called ugly by a toad.”

Steve Woods, an independent and businessman from Yarmouth, acknowledged that advertising is effective. Saying that political attack ads poured from his TV the night before, Woods quipped, “At about 4 a.m. I was ready to vote for Charlie Summers.”