Justin Trudeau is expected to announce that he will run for the leadership of the federal Liberal Party later this week. Trudeau, a Montreal MP and son of former prime-minister Pierre Elliott Trudeau, is expected to immediately become the front runner in the race to lead the party.

The younger Trudeau is undoubtedly an attractive candidate, thanks to his magnetism and youth, but the Liberals would be wrong to crown him as leader without properly putting him through his paces. That simply cannot happen without a competitive leadership race that forces Trudeau and his opponents to lay out their plans.

The races to replace former prime minister Jean Chrétien and Stéphane Dion as in 2003 and 2009 respectively, demonstrate the pitfalls of coronations: campaigns in which the leading candidate runs unopposed or has only token opposition. The victors in those races, former prime minister Paul Martin in 2003 and Michael Ignatieff in 2009, won largely without having to explain their plans for the party. This not only undermines the ability of party members to assess the candidates, but also keeps the party from reflecting on the best way forward.

By contrast, the race to replace the late Jack Layton as leader of the New Democratic Party, held earlier this year, was far more competitive. Several candidates, including the eventual winner and now leader of the opposition Thomas Muclair, were seen to be viable and presented contrasting visions of the party’s future. This allowed New Democrats, buoyed by their startling gains in the 2011 election, to have a serious debate amongst themselves about the sort of party that they wanted, and the path to follow leading up to the anticipated 2015 election.

If the Liberals are serious about renewing their party and rebuilding it into a political machine capable of winning national campaigns, they owe it to themselves to make the leadership contest a fair fight. This cannot happen unless Trudeau has to face more than the token opponents who have entered the race so far. Many prominent Liberals, including embattled Ontario premier Dalton McGuinty, former finance minister John Manley, and former New Brunswick premier Frank McKenna have declined to run. It also seems unlikely that any political outsiders, such as the much-touted Bank of Canada governor Mark Carney, could be convinced to run.

Rather, it is more likely that any challengers to Trudeau will come from within the Liberal caucus. There are several past or potential leadership candidates in the party. However, Trudeau’s entry into the race might have a chilling effect on these MPs; they may be reluctant to challenge Trudeau and jeopardize their status within an eventual Trudeau-led party.

Trudeau is a strong candidate for Liberal leadership, but that alone should not be enough to put him over the top. He needs to prove that he can rebuild the party, overcome its often-crippling factionalism and craft a message with the kind of national appeal that would allow the Liberals to outflank the New Democrats in 2015. Trudeau certainly has a lot of raw material to work with but he needs to show what he can do with it before being given the helm. Without a competitive leadership race, it is difficult to see how that can happen.