Chris Matthews is keeping his mouth shut following revelations that Hillary Clinton's major donors are also funding his wife Kathleen Matthews' run for Congress and some of those kicking in money are guests on his MSNBC "Hardball" show.Matthews has yet to offer any explanation for the alleged conflict of interest that has rocked the world of cable news, The Daily Caller reported in a story published Sunday.But MSNBC offered a terse statement that it "does not book guests on the basis of political contributions. That would violate not only our ethical obligation as journalists, but also violate the standards of NBC News."The Caller says that to date, "more than 17,000 progressives" have signed a MoveOn petition calling on MSNBC to suspend the veteran political gabber.As Kathleen Matthews, a former TV news anchor, geared up to run for the seat ofRep. Chris Van Hollen, a Maryland Democrat, her husband insisted he would respect "certain boundaries" in his coverage, but said he would still "offer Kathleen whatever help I can,"reports.