By City Hall bureau chief Mike Dunn

PHILADELPHIA (CBS) — Just three weeks remain before the May 19th Pennsylvania primary and the battle for the Democratic nomination for mayor is about to get more heated, with two more candidates launching TV and radio ads.

READ MORE: Philadelphia Weather: Fast Storm System To Bring Snow To Parts Of Delaware Valley Sunday Evening

This week brings the first broadcast ads of former City Councilman Jim Kenney and former D-A Lynne Abraham. They’re not the first, of course. State Senator Anthony Williams jumped in with his own ads last month; former PGW executive Doug Oliver last week. And independent political committees have been running ads in support of Kenney and Williams.

Randall Miller, political analyst at St. Joseph’s University, says voters should be braced for more.

“With the ad wars really starting — even though they’ve been on for a while, but they’ve been starting now — the public is going to wake up to the fact that there’s a primary coming up. We’re going to get blasted and blistered soon enough with these ads,” Miller says.

READ MORE: 21-Year-Old Critically Injured In West Philadelphia Shooting: Police

Some of the candidates have been taking relatively gentle jabs at one another on their websites and at forums. But Miller wonders when the tv and radio ads will turn negative.

“What’ll be interesting in the next couple of weeks is not just who’s up, but the tenor of the campaign,” he says. “We’ve already got some inklings that some people are now going negative on websites and this sort of thing. Whether that’s going to actually filter in to the television and radio advertising — that will be a test of what the character of the campaign will be like over the next couple of weeks.”

A spokesman for former City Solicitor Nelson Diaz says they are not yet publicly divulging their advertising plans. And a spokesman for Milton Street says they have no plans for radio and tv ads, citing fundraising difficulties in light of a challenge to Street’s nominating petitions.

Miller says the three so-called second tier candidates are in a tough bind: “They don’t have enough money to wage the big war, which is going to be on the airwaves.”

MORE NEWS: Fire Now Under Control At Center City High-Rise

A Center City businessperson, Melissa Murray Bailey, is the sole candidate for the Republican nomination.