The Republican presidential candidate Ted Cruz, already facing scrutiny for not disclosing a Goldman Sachs loan he used for his 2012 Senate campaign, also failed to disclose a second loan, from Citibank, for the same race, according to a letter he sent Thursday to federal election officials. The one-page letter said that the “underlying source†of money for a series of personal loans Mr. Cruz made to his Senate campaign in Texas included both bank loans, which totaled as much as $1 million. Both loans were “inadvertently omitted†from the required filings, the letter said. Previously, Mr. Cruz has only...