Bill S-125 would ensure that advertising bought by political parties in the three-month pre-writ period would be added to a campaign's election budget and subjected to spending limits.
In the 2011 federal election, any party that ran candidates in all ridings was subject to a spending cap of $21 million.
However, millions of dollars can be dumped into ads by political parties before an election is called and avoid the expenses ceiling.
Dawson's bill defines an election expense as the cost, or donation in kind, of a property (such as signs) or service used to promote or oppose a political party, its leader or a candidate.
A news release from the Senate Opposition — a group made up of former Liberal senators — says the bill addresses concerns raised by a former elections chief about how fixed election dates would necessitate some kind of curb on election advertising before the election period starts.
Jean-Pierre Kingsley told a parliamentary committee in 2007 that the practice of having elections every four years on a fixed date would open up a loophole allowing pre-election spending to be exempt from rules about how money is spent in elections.
Dawson, the bill's sponsor, is now an independent senator since Liberal Leader Justin Trudeau kicked all Liberal senators out of the Liberal caucus.
Conservatives will respond
It's not clear how the Conservative-dominated Senate will respond to Dawson's bill.
The Conservatives' Fair Election Act, introduced last week, actually freed up a portion of election spending from being subjected to any limits.
In the election reform act, which is now being studied by a parliamentary committee, phone calls or other electronic communications to previous donors on behalf of a party will no longer count as an election expense.
Attempts to skirt election spending limits have been the subject of controversy.
In the 2006 election, the Conservatives utilized a so-called "in and out" scheme that allowed some expenses to get around the spending limit.
The "in and out" arrangement saw $1.3 million move between the bank accounts of the national Conservative party and local riding associations in order to buy advertising during the election.
Several senior Conservatives were charged by Elections Canada for exceeding spending limits. In 2011 the Conservative Party agreed to pay a fine of $52,000 and the charges against individuals were dropped.