The saber-rattling around Initiative Petition 28, the proposed tax increase on large corporations, got louder today.

Opponents of the measure, which would impose a gross receipts tax on companies with more than $25 million in Oregon sales, and is projected to raise $3 billion a year, disclosed their first batch of contributions and it's impressive.

The group, which calls itself Defeat the Tax on Oregon Sales, reported 506 contributions totaling $5.27 million. In past ballot measure battles, Oregon's business community has not always raised money well or spent it effectively.

Whether the group will spend effectively this time is an open question, but the long list of contributors, many of whom are newcomers to Oregon ballot measure fights, suggests there's plenty more money coming.

The campaign reported 43 checks of $50,000 or more, with 18 of them coming from out of state. The out-of-state part is unsurprising because the measure is aimed at big companies headquartered elsewhere, although the measure will also affect many Oregon companies.

Among the big, deep-pocketed donors so far: Automobile Dealers Association of Portland ($250,000), the oil company Phillips 66 ($217,000), Comcast ($150,000), Kroger/Fred Meyer ($125,000), Costco ($125,000), Progressive Insurance ($72,000), Cargill ($61,000) and a slew of others.

The proponents, the A Better Oregon Committee, have reported raising $338,000 this year and have just $13,000 on hand but will probably soon begin reporting large contributions from the union backers of IP 28.