WASHINGTON (Reuters) - The head of the U.S. Office of Government Ethics, who clashed with President Donald Trump and his administration, said on Thursday he would resign before his five-year term ends in January to take a new job. In a letter to Trump dated on Thursday and posted on his Twitter account, Walter Shaub said he would step down from the ethics watchdog effective July 19 and praised his staff for their commitment to laws and ethical principles over private interests.      Shaub has sounded many alarms over the Trump administration’s business entanglements. He urged Trump to divest from his business empire rather than turn management of it over to his sons, and chastised the White House for not disciplining presidential advisor Kellyanne Conway after she endorsed a fashion line sold by Ivanka Trump, the president’s daughter. Shaub said in an interview with the Washington Post published Thursday that he was not pressured to leave, but felt that he could not achieve more in the ethics office under the Trump administration. Democratic lawmakers lauded Shaub’s service. Chuck Schumer, the top Senate Democrat, said he looked forward to examining Republican Trump’s nominee to replace Shaub. Schumer said he hoped the successor would prevent lobbyists and private interests from “rigging the system against working families under the cover of darkness.” Elijah Cummings, the top Democrat on the House Oversight and Government Reform Committee, urged the Republican chairman of the committee to invite Shaub to testify to the panel about necessary ethical reforms. Some Republican lawmakers, such as Cummings’s former Republican counterpart, Jason Chaffetz, had little praise for Shaub during his tenure. Chaffetz rebuked Shaub in a January letter for making public statements about Trump’s finances. Shaub will next head the Ethics Practice at the Campaign Legal Center, a Washington-based nonpartisan group dedicated to democratic reform, said Larry Noble, the group’s general counsel.  Noble said that the Center learned of Shaub’s interest in leaving his government job in the last two weeks and seized the chance to hire him. Shaub’s work at the Campaign Legal Center will involve examining deficiencies in existing ethics laws and developing ways to strengthen them, both at the Office of Government Ethics and in the realm of congressional ethics, Noble said. 