"Words calculated to catch everyone may catch no one," said US Democratic presidential candidate (twice unsuccessful) Adlai Stevenson.

Different countries. Different times. Different men.

On the face of it, there are no reasons why Bill Shorten should draw on the considerable wisdom of Mr Stevenson — a man often described as the best politician never to become president of the United States.

But then, there are plenty of reasons why he should.

Labor's "official" campaign launch and final two-week surge to polling day are Mr Shorten's last best chance to catch the substantial number of votes he will need to become Australia's 30th prime minister.

In the last six weeks, Mr Shorten has expended many words in the hope of catching many people; "trust" Labor on "Medicare", "climate change", "multinationals paying their fair share" and "budget repair that's fair".

They are (to borrow from Mr Stevenson) words calculated to catch everyone — but there are also indications they have not caught enough.

Australian campaign launches, at their best, touch-off a rallying call that captures and defines the mood of a nation; "It's time!" (1975), "we will decide who comes to this country" (2001), "this reckless spending must stop" (2007).

At their worst, they are tedious re-statements of tired lines retold to the party faithful in Sunday morning broadcasts few Australians will bother to watch in their entirety.

Polls and seat analysis of both major parties suggest Mr Shorten's speech today must do less of the latter and more of the former — to somehow stir, inspire and "catch" the wavering voters of 21 seats. It is a tall order.

Public transport infrastructure for Brisbane, Sydney and Melbourne were among the new commitments made today.

While doubtless worthy in their own right, nothing about infrastructure promises quite lends itself to the sort of game-changing, stirring oration that Labor, as the self-described "underdogs" of this election, seem to need.

Labor campaigners set modest expectations for their launch.

It is, they say, a final set-piece event to complete before moving into a higher tempo of operations in the final fortnight.

Much rests for Labor and for its leader on regaining momentum in the time remaining.

Unlike Mr Stevenson, who lost in his first tilt at the presidency and got a second chance four years later, the ALP has proven itself less likely to give a defeated leader another shot.