Possibly Brown could have won, but Smith was almost a foregone conclusion in 1992.
Assuming Brown defeats Smith, given the Tory travails he goes on to win in 1992 but he doesn't capture the public imagination to anywhere near the extent that Blair did in the OTL, and although he does create something akin to New Labour it is a more cosmetic branding than in the OTL.
Labour majority of about 70. Portillo holds his seat and becomes opposition leader. Blair is Foreign Secretary and harbours ambitions for the premiership which cause tensions between him and Brown. Robin Cook is Chancellor and Margaret Beckett Home Secretary and Deputy PM.
Labour wins again in 2001 but only by 15-20 seats. Darling becomes Chancellor. Blair is demoted to Environment to make way for Cook and, furious, finds an excuse to resign the following year. A fractious party becomes divided between supporters of Brown and Blair. After a disastrous result in the 2004 Euro elections and dreadful opinion polls for Brown, he resigns rather than lead Labour to a seemingly inevitable defeat in 2006. Blair defeats Darling for the leadership and reverses the opinion poll decline to some extent and calls an early election to capitalise.
The 2005 election produces a hung parliament with Labour the largest party by almost 50 seats. Blair and Kennedy form a coalition, with the withdrawal of troops from Iraq one of Kennedy's main demands.
David Cameron is elected leader of the opposition. After five years of increasingly fractious Lab/Lib coalition which does not suit Blair's temperament, the Conservatives win a narrow majority in the 2010 election.
Blair resigns from the leadership and from Parliament, and in a satisfying result for his old rival Gordon Brown, Ed Miliband, who promises a break with the recent past becomes Labour leader.