Federal regulators are asking Texas Attorney General Ken Paxton’s U.S. Senate Campaign to explain or return roughly $658,000 in political contributions that appear to violate federal law.  The Aug. 17 letter from the Federal Election Commission gives the Ken Paxton for Senate campaign a little more than a month to justify five pages worth of second-quarter contributions that — as recorded in its paperwork — exceed federal limits on how much individuals donors can contribute. Under federal law, individuals are barred from making contributions to a candidate that exceed $3,500 per election.