Premier Gordon Campbell didn’t bill it as the 10 Commandments.

But his economic address tonight was clearly designed to prevent two B.C. Liberal by-election candidates from wandering in the political desert for the next 40 years.

The timing of the premier’s speech—which included 10 “key actions”—couldn’t have been better for Arthur Griffiths and Dr. Margaret MacDiarmid, who are running as B.C. Liberal candidates in Vancouver-Burrard and Vancouver-Fairview, respectively.

On Wednesday (October 29), Griffiths squares off against New Democrat Spencer Herbert in the downtown constituency that Lorne Mayencourt held by a hair in 2005. MacDiarmid faces New Democrat Jenn McGinn in a west side constituency that Gregor Robertson narrowly won in 2005.

The Greens are running their leader Jane Sterk in Vancouver-Fairview, and their vice chair Drina Read in Vancouver-Burrard.

If the B.C. Liberals lose both by-elections to the New Democrats, it will give NDP Leader Carole James and her caucus tremendous momentum moving toward the general election in May, 2009.

Don’t kid yourself. By-elections are important on the eve of a general election.

In 2004, the NDP won a landslide victory in Surrey-Panorama Ridge, which helped the party marginalize the Greens and eventually take 33 seats in the 2005 general election.

In 1981, the Social Credit won an upset win in Kamloops, which strengthened the party as it headed toward the 1983 general election.

A by-election win can motivate campaign workers, encourage donors to contribute more money, and influence subsequent media coverage.

Campbell's announced actions—which included a three-percent personal-income-tax cut retroactive to January and a 2.5-percent small-business tax cut effective January 1—were probably cooked up in part to give the B.C. Liberals a boost in the upcoming by-elections.

His promise to provide unlimited deposit insurance in B.C. credit unions (previously, deposits were guaranteed up to $100,000) is another vote getter for wealthier residents, many of whom are more likely to vote Liberal.

The problem for Campbell is that a by-election offers an opportunity to voters to express their disapproval of him without worrying about any change in government.

And for that reason, the premier's 10 Commandments probably won’t be enough to roll back the NDP tide next Wednesday.