WASHINGTON (AP) — Rick Gates’ guilty plea to federal conspiracy and false-statements charges turns him from defendant to cooperating witness in the special counsel’s probe of President Donald Trump’s election campaign and Russia’s interference. The plea by Gates, a former senior adviser to President Donald Trump’s election campaign, revealed he will help special counsel Robert Mueller’s investigation in “any and all matters” as prosecutors continue to probe the 2016 campaign, Russian meddling and Gates’ longtime business associate, one-time campaign chairman Paul Manafort. With his cooperation, Gates gives Mueller a witness willing to provide information on Manafort’s finances and political consulting work in Ukraine — and someone who had access at the highest levels of Trump’s 2016 presidential campaign.