WASHINGTON — The two men share a passion for unbridled markets, concerns about the Internal Revenue Service and a skeptical view of climate change.

Now the two — Senator Ted Cruz, Republican of Texas, and Robert Mercer, a Wall Street hedge-fund magnate — share another bond that could link them through November 2016: Both want to see Mr. Cruz elected president.

Mr. Mercer, a reclusive Long Islander who started at I.B.M. and made his fortune using computer patterns to outsmart the stock market, emerged this week as a key early bankroller of Mr. Cruz’s surprisingly fast campaign start. He is believed to be the main donor behind a network of four “super PACs” supporting Mr. Cruz that reported raising $31 million just a few weeks into his campaign.

The emergence of rich and relatively low-profile donors like Mr. Mercer could single-handedly jump-start a presidential campaign, said Trevor Potter, a campaign finance lawyer who served as a Republican member of the Federal Election Commission.