By Seema Mehta, Los Angeles Times (TNS)

The self-described “joyful tortoise” in the race for the GOP presidential nomination is more angry than happy these days.

Former Florida Gov. Jeb Bush, who promised an optimistic campaign focused on his record rather than attacks on his rivals, has departed from that approach and begun to forcefully confront front-runner Donald Trump.

Last week, Bush’s campaign released a video and an online quiz targeted at Trump supporters that played up Trump’s past support for abortion rights, universal health care and Democratic candidates, including front-runner Hillary Rodham Clinton. The quiz also got personal, going after Trump’s well-known phobia of germs.

“The man is not conservative,” Bush told reporters in Miami on Tuesday. “Besides, he tries to personalize everything. If you’re not totally in agreement with him, you’re an idiot or stupid or don’t have energy or blah blah blah.”

That’s a notable change in posture and tone for a candidate who is better known for his cerebral, wonky manner than his swagger. The shift is driven by Trump’s relentless and personal needling of Bush, whom he described Thursday as a “very low-energy person” and “a little bit sad,” as well as Trump’s unexpected and continuing dominance in the polls.

Trump goes after most of his Republican rivals, but seems to especially enjoy poking at Bush, for whom he once hosted a fundraiser at Trump Tower in Manhattan.

On Wednesday, Trump criticized Bush for speaking Spanish at a news conference. “He should really set the example by speaking English while in the United States,” he told Breitbart News. Trump has retweeted a critic who said Bush “has to like the Mexican Illegals because of his wife,” who was born in Mexico.

Trump trolls Bush on social media, arguing that the candidate is ashamed of his last name and highlighting that former firstlLady Barbara Bush said in 2013 that the nation had had “enough Bushes” as president.

“Mother knows best, Jeb!” Trump said on that post, on Instagram. Trump’s campaign did not respond to a request for comment.

Political observers say Bush was forced to act, because of Trump’s leading status and the sustained, personal nature of his attacks.

“At a certain point, you have to respond. Because if you don’t, you look like you’re a punching bag,” said Tim Hagle, a political science professor at the University of Iowa. Bush has fallen to sixth place in an aggregate of recent polls in Iowa, which holds the first nominating contest in the nation.

Hagle noted that some of Bush’s supporters had expressed concern over whether the wonky candidate, who hasn’t run for office since 2002, could deal with the slashing nature of modern-day politics. “He’s got to show he has some fight in him,” Hagle said.

It’s a question that dogged Bush’s father, former President George H.W. Bush, noted Jack Pitney, a government professor at Claremont McKenna College and a former national GOP official. The nation’s 41st president had been the subject of a 1987 Newsweek cover story that said the then-vice president was “fighting the ‘wimp factor.'”

“Now the younger Bush has to prove that he’s not a wimp,” Pitney said. The father fought back with pointed attacks on his rivals and the media, but Pitney questions whether that that is enough to tackle Trump, whose draw for voters is based more on personality than his record. “I’m not sure that the attack on Trump’s consistency is going to work. People are supporting him not because of consistency but because of brassiness.”

Brassiness is not a quality that has ever been associated with Jeb Bush, who lacks the Texas-twanged charisma of his brother, former President George W. Bush.

The new vigor — for a candidate who has enviable advantages in fundraising but has floundered in the polls — is purposeful and will continue, according to Bush campaign spokesman Tim Miller.

“Increasingly it has become clear that Trump was going to run a legitimate campaign so he’s being treated as a legitimate candidate. Part of that is contrasting Gov. Bush’s proven conservative record with Donald Trump’s past as a New York liberal,” Miller said. “This is going to be a sustained attack, a sustained campaign from Gov. Bush, to highlight the differences between him and Mr. Trump.”

Bush’s supporters appreciate the turn.

“In many ways, Donald Trump is a gift to Jeb Bush because he perfectly provides a very clear contrast to Jeb’s record of conservative reform and accomplishment in Florida,” said Paul Lindsay, spokesman for the Right to Rise USA super PAC, which has raised more than $100 million to back Bush’s bid but is legally not allowed to coordinate with his effort. “The campaign is capitalizing on that, and rightly so.”

The super PAC paid for an airplane to carry a banner reading “Trump 4 higher taxes. Jeb 4 Prez” over a August Trump rally in Alabama but has focused its efforts on biographical television ads introducing Bush to early-state voters. Lindsay said the group would not rule out future defensive action.

“We certainly reserve the right to defend Gov. Bush’s record and contrast it with all the other candidates in the race, including Donald Trump,” Lindsay said.

(c)2015 Los Angeles Times. Distributed by Tribune Content Agency, LLC.

U.S. Republican presidential candidate Jeb Bush answers a question from the audience during a campaign town hall meeting in Laconia, New Hampshire September 3, 2015. REUTERS/Brian Snyder