Dino Rossi, a marquee name for Washington Republicans ever since his oh-so-close loss for governor in 2004, plans to jump into the U.S. Senate race on Wednesday, according to media reports.

His entry into the race against three-term Democratic Sen. Patty Murray, one of the Senate’s most powerful senior members, comes unusually late for a challenger.  Filing Week is now less than two weeks away, and ballots for the Top 2 Primary go in the mail July 30.

Rossi’s decision would not be surprise, however. He has been dropping broad hints that he would take on Murray, most recently at the weekend Cascade Conference at Sea-Tac.   He has been close to Murray in most of the recent polls, including the nonpartisan Washington Poll released Monday that showed Murray at 44 percent and Rossi at 40 percent, within the margin of error.

Rossi, a real estate investor and former state Senate budget chairman, came within 133 votes of Gov. Chris Gregoire in 2004, losing only after three tallies and a court contest that lasted half a year.  He did less well in a rematch in 2008.

A long list of Republicans have lined up to challenge Murray, including state Senator and former state GOP Chairman Don Benton and former pro footballer Clint Didier.  Both have said they’d stick with the race even if Rossi got in.

The Rossi development, including campaign officials who have been brought aboard, was first reported by Politico, the national political blog, AP and homestate media.  The Rossi camp would confirm only that an announcement is planned for mid-week.