Former President Donald Trump recently made a controversial proposal to a gathering of oil executives and lobbyists at his Mar-a-Lago residence in Florida: Favorable policy in exchange for $1 billion in campaign cash. Now, it looks as if the U.S. Senate may launch an official inquiry into the ex-president. That’s according to the New Republic’s Greg Sargent, who spoke to Sen. Sheldon Whitehouse (D-Rhode Island) about Trump’s recent entreaty to the oil industry. Whitehouse said it was “highly likely” that the Senate Budget Committee would investigate the former president over his brazen offer. …