The televised debate starts at 6:30 p.m. on Global stations across the province, as well as radio stations CHED and CHQR.
Voters have a chance to see how the leaders perform under pressure and where they stand on issues.
There are no appearances scheduled for any of the leaders today, except for the debate.
Conservative Leader Jim Prentice is facing criticism that the budget he said was so important it needed an election to ratify is nothing more than a promise list.
Alberta NDP Leader Rachel Notley, David Swann of the Liberals, and the Wildrose party levelled the accusations after Prentice rolled back on a key budget plank to save $90 million by reducing charity tax credits.
Prentice had previously stood firm on his budget, saying it was a difficult but necessary document to fix Alberta's finances.
Since then he has also announced he would axe a quarter of Alberta's 320 boards, agencies and commissions by the end of the fiscal year.
The budget has been introduced in the legislature but has not been debated or passed.
It hikes taxes almost across the board except for corporations while cutting or freezing departmental spending and delivering a $5 billion deficit this year.
Prentice called the election for May 5, a year earlier than directed by law.