Washington - After six months of infighting, investigations and legislative failures, President Donald Trump is trying to combat new signs of weakness in his Republican base and re-energise his staunchest supporters.White House officials have been urging the president to refocus on immigration and other issues that resonate with the conservatives, evangelicals and working-class whites who propelled him to the Oval Office. The president has ramped up his media-bashing via Tweet, long a successful tactic for Trump, and staged rallies hoping to marshal his base to his defence.The effort underscores Trump's shaky political positioning not yet seven months into his presidency.Trump has remained deeply unpopular among Democrats, and there are signs that his support among Republicans may be softening. His advisers are aware that a serious slip in support among his core voters could jeopardise hopes for a major, early legislative accomplishment and would certainly increase Republicans' worries about his re-election prospects.'Slightly' downWhite House counsellor Kellyanne Conway acknowledged the concerns on Sunday on ABC, saying the president's approval rating "among Republicans and conservatives and Trump voters is down slightly". "It needs to go up," she said.In a Monday morning tweet, Trump dismissed his adviser's statement. "The Trump base is far bigger & stronger than ever before," he wrote on Twitter. The Trump base is far bigger & stronger than ever before (despite some phony Fake News polling). Look at rallies in Penn, Iowa, Ohio.......— Donald J. Trump (@realDonaldTrump) August 7, 2017He later insisted that his support "will never change"! But polling doesn't support Trump's claim. Just one-third of all Americans approved of his job performance, a new low in the poll.The president's struggles already have prompted public speculation about his political future. The White House pushed back angrily on Sunday against a New York Times report about Republicans preparing for 2020 presidential race that may not include Trump. The report described Vice President Mike Pence as laying groundwork in case Trump does not run. Pence called the report "disgraceful".The chatter has been fuelled by Trump's unsuccessful attempt to shepherd health care legislation through Congress, the drip-drip of revelations about his associates' ties to Russia and the churn of turnover and turmoil at the White House. The president's advisers have tried to drown out the bad news by focusing on his agenda.Alice Stewart, a conservative who worked for the presidential campaigns of Senator Ted Cruz and former Arkansas governor Mike Huckabee, said Trump is right to make overtures toward his coalition of loyal supporters, even if some of his moves are incomplete."I think people realise half a loaf is better than none," Stewart said.