When the technology investor Peter Thiel takes the stage just before Donald J. Trump at the Republican convention this week, he will become the most prominent public face of a species so endangered it might as well be called extinct: the Silicon Valley Trump supporter.

Nobody knows what Mr. Thiel, a co-founder of PayPal, will say (he declined an interview), but in the tech industry, his appearance at the convention is being greeted with more apprehension than excitement. Venture capitalists have a special term for investment opportunities that offer the potential for a big return but also carry a great deal of risk: high beta. For Silicon Valley's political aspirations, Mr. Thiel's speech is the ultimate high-beta performance.

On the one hand, an emissary from tech will have a national platform to push the industry's agenda and, more important, its worldview. By the end of Mr. Thiel's speech on Thursday night, it's possible he will have succeeded in showing off an ideology that is rarely encountered in public — the hands-off-my-stuff, techno-libertarian vision that is a hobbyhorse of Mr. Thiel and a few other Silicon Valley bigwigs.

And if Mr. Trump wins the White House, Mr. Thiel will have a direct line to a chief executive who hints at a penchant for making big things happen for his supporters. In 2004, Mr. Thiel made a $500,000 investment in Facebook, the earliest big bet on what was then one of many social networks. Facebook succeeded beyond anyone's guess, and Mr. Thiel's half million turned into close to half billion; he now sits on the company's board. In some ways, the bet on Mr. Trump is a similar long-shot play that could pay off "big league," as the Republican nominee might say.