Pharmacare is poised to become an election issue in Ontario, with Premier Kathleen Wynne promising free prescription drugs for children and young adults in Thursday's budget, and the NDP rolling out its own version earlier this week,

The two drug programs differ in some key aspects, but they share a crucial political effect: putting the Progressive Conservatives and their leader Patrick Brown on the spot.

Voters are likely to compare the NDP and Liberal plans to see how they measure up, and for now will just have to wonder what the PCs will propose.

"I would have a drug access plan that is fair," Brown told reporters during a news conference Thursday, but offered no specifics. "Of course everyone wants greater drug coverage. The question I would ask is, I want to make sure those precious taxpayer dollars are going to the people that really need it."

The NDP's drug plan, which it unveiled on Saturday, would cover people of all ages, but would only include 125 different types of prescription medication.

Ontario NDP Leader Andrea Horwath promises her party will create a provincial pharmacare plan that covers everyone if elected in 2018. (CBC)

The Liberal drug plan, laid out in Thursday's budget, would only cover people age 24 and under, yet would cover some 4,400 medications — every prescription drug covered by the existing Ontario Drug Benefit Plan for seniors and people with lower incomes.

"There are many people who can't afford to buy the drugs that are prescribed for their kids, so that's why we're making this change," Wynne told CBC Toronto News host Dwight Drummond in an interview Thursday.

"It's about providing pharmacare for more people, and what better way to start than with our most vulnerable," Ontario Finance Minister Charles Sousa said Thursday in a news conference.

NDP Leader Andrea Horwath dismissed the Liberal plan as a "half measure."

"This small measure that the government has put forward in the budget isn't nearly what it should be," Horwath told a news conference Thursday. "All I can think of is they made it up on the back of a napkin."

'Why cover rich kids' drugs?'

The NDP's plan will, of course, only come to pass if the New Democrats win the 2018 election. Meanwhile, the Liberals will roll out their drug plan in January, six months before Ontarians go to the polls.

That will give them an advantage: not just in campaigning on a promise of pharmacare, but because voters will see how the plan works. Lots of voters, too: there are four million children and young adults under the age of 25.

The Liberals are defending their decision to make the drug plan open to everyone in the age group, regardless of family income. During Thursday's news conference, a reporter asked "Why should a millionaire's child have their drugs covered by taxpayers?"

"You want to income test, and we're not doing that when it comes to our children," Sousa replied. "Universal health care applies to everybody equally."