After a tumultuous stretch since accepting the GOP presidential nomination last month, Donald Trump tried this week to broaden his appeal to a wider swath of the electorate, aiming to&nbsp;sow the seeds for a competitive fall race with Hillary Clinton.Trump shook up his campaign leadership, launched television ads, gave one of the best speeches of his candidacy and visited flood-ravaged Louisiana. But by making such moves fewer&nbsp;than 100 days before election day, an open question remains about whether he has enough time to capitalize on them."As a Republican, you have virtually no margin of error,&nbsp;and Trump&rsquo;s campaign is nothing but errors,"&nbsp;said GOP strategist Reed Galen, who worked for former President George W. Bush. &ldquo;They sort of tumble from one thing to the next really without much thought to where, when and how it&rsquo;s going to happen.&rdquo;Galen pointed to the Friday announcement that Trump&rsquo;s campaign manager Paul Manafort had resigned. Instead of news coverage focusing on the well-received speech Trump delivered the night before, or his low-key tour of the flooding in&nbsp;Louisiana, Manafort dominated the headlines.