washington democrat hillary clinton suddenly vulnerable presidential race pressure deliver strong performance republican donald trump first debate monday moment could consequential yet 2016 election political veterans involve prepare past presidential debate say clinton drive home would run country uncertain time draw contrast steady experience alternative untested trump part trump need show enough gravitas convince skeptics ready commander chief say 90-minute face-off hofstra university hempstead new york first three debate take place time clinton once-comfortable lead opinion poll former reality tv star evaporate history show single bad debate performance alter trajectory u.s. presidential race reuters/ipsos poll show 20 percent electorate remain undecided far high stage campaign 12 percent undecided four years ago tv audience debate expect record easily surpass record 46.2 million households watch first encounter president barack obama republican mitt romney 2012 accord nielsen rat company go best communicate clearly fearlessly face insult attack bully bigotry see come opponent clinton say tuesday steve harvey radio show anita dunn help president barack obama prepare debate republican nominee john mccain 2008 say obama succeed first debate steer conversation repeatedly back struggle u.s. economy even though event suppose foreign policy say expect clinton try exploit trump weaknesses emphasize strengths contrast want hone say debate best opportunity two candidates widely see voters untrustworthy put rest question fitness white house nov. election fast approach even candidates body language closely scrutinize past elections brett donnell debate coach help president george w. bush 2004 debate mccain 2008 say bush put necessary work first debate democrat john kerry year show quickly put defensive bush blink rapidly slouch behind lectern kerry judge winner bush get serious debate donnell say clinton shaky performance sept. nbc commander-in-chief forum become prickly response question handle classify email serve u.s. secretary state presentation important hillary work presentation commander-in-chief forum good come likeable come sour defensive donnell say clinton spend week debate preparations small circle top aid home chappaqua new york clinton aid say prepare two scenarios one trump measure serious another freewheel make inflammatory personal attack trump rely famed spontaneity fire one-line zingers dismantle 16 republican rival primaries dispatch low-energy jeb bush lie ted cruz little marco rubio repeatedly call clinton crook hillary rally sure go show say jennifer palmieri senior adviser clinton may aggressive may lay back hard game necessarily would say focus point want make trump supporter republican u.s. representative chris collins new york say trump understand need put forth presidential demeanor think seriousness understate go see debate prep make sure go able pull somehow message say rick lazio republican former congressman new york find clinton tough opponent face u.s. senate debate new york 2000. see bully lose debate election say trump need treat clinton carefully avoid sense name-calling highly disrespectful badger anything like say role-playing former republican senator judd gregg play democrats al gore john kerry george w. bush mock debate sessions 2000 2004 say bush begin prepare early june unbeknownst news media two practice sessions day reason say suspect trump preparation work let believe something would foolish go practice hear line say republican source close campaign say former fox news chief executive roger ail coach trump former reality tv star want over-prepared trump spokesman jason miller say trump prepare debate nobody play role hillary clinton mr trump prepare everything say trump vs. clinton debate mark big moment election