Will we see a presidential spoiler in November?

Could the Libertarian Party ticket of Gary Johnson and the Bay State's own William Weld effectively doom GOP presidential candidate Donald Trump's chances in November?
Pundits have hemmed and hawed at this question, drawing comparisons to the Green Party's 2000 presidential ticket of Ralph Nader and Winona LaDuke. The Nader-LaDuke tandem, as has been noted, reeled in 97,488 votes in Florida — a state which effectively swung the 2000 presidential election and a state where Republican George W. Bush defeated Democrat Al Gore by a scant 537 votes.