TAMPA -- In a move that was widely expected, Tampa Mayor Bob Buckhorn threw his support in the race to succeed him behind Jane Castor, who served his administration as police chief and emerged Tuesday as the top vote-getter in Tuesday’s citywide election.

Why did Buckhorn wait until Wednesday to issue his endorsement in a months-long race that drew seven candidates?

“It’s important that we sorted out the field," he said during a news conference Wednesday morning at Water Works Park. "I had no doubt that Jane would be in the runoff.”

Castor received 48 percent of the vote, just shy of the 50 percent plus one that would be needed to win the election outright. She faces an April 23 runoff election against the No. 2 finisher, philanthropist and retired banker David Straz. Straz received 15.5 percent of the vote.

Related: Jane Castor will face David Straz in Tampa mayor’s race

Buckhorn, who is leaving office because of term limits, said Castor, 59, is the only candidate in the race who can continue the path he has set for the city.

The admiration was mutual.

"This transformation has been an American story,” Castor said. “The trajectory that Bob Buckhorn has put the city on has been truly amazing.”

She said this is no time for Tampa to slow down: “We’ve got to put our foot on the gas and keep going.”

Only when reporters asked did Castor or Buckhorn discuss Straz.

Asked whether Straz should withdraw from the non-partisan race, with less than a third of the votes Castor received, Buckhorn said, “That’s only a decision Mr. Straz can make.”

The Straz campaign confirmed Wednesday that he will not drop out of the race.

Asked whether they expect her challenger will resort to negative campaigning to make up the huge voter deficit, Buckhorn said, “People in the community want to be inspired and not divided. If you have a plan run on it. Tearing down an opponent is not a strategy to win.”

Castor said she will defend herself if necessary.

“People here in Tampa want a leader," she said. "I will remain positive.”

Straz has scheduled a media availability for 3 p.m. at Julian B, Lane Riverfront Park, a $35.5 million project that Buckhorn considers a legacy project and one that Straz has criticized repeatedly as a waste of money.

So far, Straz has outspent the entire field of candidates combined, pouring about $3 million into a campaign that garnered him 7,518 votes to Castor’s 23,318.

Buckhorn and Castor said they expected most of the candidates eliminated Tuesday will endorse Castor. Buckhorn specifically mentioned Harry Cohen, Dick Greco Jr. and Ed Turanchik.

Greco Jr. told the Tampa Bay Times later Wednesday that he called Castor Tuesday night to congratulate her and offer his support for the runoff. Greco received 4,156 votes equaling 8.55 percent.

One candidate not mentioned was City Council member Mike Suarez, who finished sixth in the race with 5 percent of the vote. He said Wednesday that he likely won’t be throwing his support behind any candidate soon.

“I’ve given up politics for Lent,” said Suarez.

Castor also pledged Wednesday to continue dying the Hillsborough River green off Curtis Hixon Park for St. Patrick’s Day, a signature tradition started by Buckhorn, who is of Irish heritage.

The mayor replied, “That seals the deal."