She wasn't, however, as equivocal when asked about a Liberal-NDP alliance.
Her remarks — using a phrase she credited to a colourful former New Democrat, the late Peter Kormos — come after she was hammered by the Liberals with accusations she would support a Tory minority government.
She has been asked for days at news conferences whether she would rule out formal coalitions or propping up either the Liberals or the PCs if they win the election but fall short of a majority.
Horwath has said she could not support Hudak's plan to cut 100,000 public sector jobs, nor would she support "corrupt" Liberals, though she hadn't explicitly ruled out any scenario until Tuesday.
"I'm going to say very clearly: I call bullspit on the idea that we will have a coalition with Tim Hudak," Horwath said at an early-morning rally in Essex.
Horwath was spending one of the final days of the campaign on a swing through southern and southwestern Ontario, with stops in Essex, London, Brantford and Waterloo.
At her second stop of the day, Horwath was asked if she would also like to call "bullspit" on the idea that she would form a coalition with the Liberals.
"Ms. Wynne has been grasping at straws the last couple of days and she's saying all kinds of things that really are not true," Horwath said in London. "So I really do need to make it clear that that rumour that she's spreading or that desperate attempt she's making to try to tell people something that's not true is useless and it's not true and it is bullspit."
In a minority government — polls suggest that's a likely outcome, either for the Progressive Conservatives or the Liberals — the NDP would have to find some common ground with the winning party, or risk plunging the province into yet another election.
Horwath is not saying what she would do if one of the other two parties wins a minority government, but she was asked what makes her think such a government could survive.
"I think New Democrats have shown how much we respect decisions that voters make," said Horwath, who propped up a minority Liberal government for years.
"We did everything we could to work on behalf of Ontarians and to focus on their priorities and to get things done for them through the last couple of years. They will make a decision on Thursday. I can't presuppose what that decision is going to be. I certainly respect their opportunity to make that decision and I will do what needs to be done to deliver for Ontarians."
Horwath said she trusts that people will elect a government that "makes sense for the people" — one of the NDP's election slogans.
Minority governments aren't as stable as majorities, as they don't have enough seats to have the power to control the outcome of votes. Every time there's a confidence vote — such as a budget or a speech from the throne — and if it doesn't pass, it can trigger an election.
But if the other two parties form an alliance, the lieutenant-governor can decide that they have the confidence of the legislature and allow them to form a government. A formal coalition government sees the supporting party get ministers in cabinet.