More than five hundred people are expected to pay tribute to state Sen. Charles J. Colgan (D) in Manassas on Saturday night at the first anniversary gala honoring the longest-serving senator.

Colgan, who had indicated that he probably would not run for reelection but may be having second thoughts, will be honored at the Hylton Performing Arts Center.

He has said that he has twice before decided not to run again for his seat, only to be persuaded first by Gov. Mark R. Warner (D) and then Gov. Timothy M. Kaine (D) to reconsider.

Warner, now a U.S. senator, will attend Saturday, as well as current and former legislators, supporters and friends. He will be honored at a dinner featuring a video tribute.

Funds raised Saturday will establish the Senator Charles J. Colgan Community Arts Benefit Fund, which which will help make the Hylton Center and its resources available to local and regional performing arts groups throughout Prince William County and the greater Washington area.

Colgan, 84, a state senator since 1976, heads the Senate Finance Committee. He did not return a phone call Friday.

“What this guy has done for that county is unbelievable, from roads to buildings,’’ Senate Majority Leader Richard L. Saslaw (D-Fairfax) said. “It’s one thing after another. The guys eats and breathes Prince William County.”