Nevada billionaire Sheldon Adelson helped shape the Republican presidential primary by pouring millions into a Super PAC supporting Newt Gingrich. Now he's poised to transfer his largesse to Mitt Romney.

POLITICO's Ken Vogel reported last week that Adelson had discussed the possibility of giving at least $1 million to the pro-Mitt Romney Restore Our Future Super PAC. He's expanded that story in an email to colleagues, writing that Adelson associates have told him the casino mogul could contribute as much as $10 million.

That sounds like an astonishing amount, but it's still less than the sum Adelson spent to prop up Gingrich's flagging presidential bid. Sheldon and his wife, Miriam, gave more than $20 million to the organization, and Sheldon had been crucial in funding the political action committee that laid the groundwork for Gingrich's campaign.

Super PACs can spend unlimited amounts of money on supporting or attacking candidates (that mostly means advertising) so long as they do not coordinate with a candidate. 

Donations directly to a candidate are a different story, but Romney has also enjoyed the support of big spenders there. An analysis of campaign data running through April found that Romney far surpassed President Obama among candidates who gave the $2,500 maximum, while Obama was ahead among supporters who gave less than $200.