Wisconsin Gov. Scott Walker says she’s old. Kentucky Sen. Rand Paul says she’s a loser. Operatives for New Jersey Gov. Chris Christie whisper that he’s not afraid of her.

For Republicans eyeing a run for president in a crowded 2016 field, one measure matters above all others: How they stack up against Hillary Rodham Clinton.

“It would almost be political malpractice not to” go after Clinton, said former Mississippi governor Ronnie Musgrove (D), who is close to Clinton and her husband.

As the prohibitive front-runner for the Democratic nomination, Clinton is the Goliath to all the would-be Davids. Attacking her is an easy way to impress donors, get noticed by potential supporters and the news media, and stand out among a growing throng of Republicans who have middling fame compared with hers.

The Republican National Committee and America Rising, a GOP super PAC, have each launched opposition-research efforts aimed at identifying lines of attack on Clinton. The RNC has already deployed a team of 10 operatives to Arkansas — where former president Bill Clinton was governor — and elsewhere to dig up fresh dirt on Hillary Clinton.

“She’s the 800-pound gorilla in the room,” said Brian Jones, a communications adviser to John McCain’s 2008 campaign and Mitt Romney’s 2012 campaign.

But there are risks for Republicans. The attacks, already in full swing two years ahead of the election, could become repetitive or tiresome. Or sexist: Swipes at Clinton’s age or health could backfire on a GOP field that is, at this point, all male.

Party leaders, however, say they relish a fight with the former secretary of state, who remains a polarizing national figure and has seen her approval ratings fall since leaving the State Department. RNC Chairman Reince Priebus said the party is treating Clinton as the presumptive Democratic nominee, no different from if she were an incumbent.

“There’s no person in America I’d rather be running against than Hillary Clinton,” Priebus said. “When it comes to raising money, unifying our party and recruiting a lot of volunteers, Hillary Clinton is my best asset.”

For now, Clinton is remaining above the fray, and her aides did not respond to requests for comment on the GOP attacks. Advisers close to her say that if she runs, there will be plenty of time to engage Republicans on her terms. Clinton leaves it to surrogates to mount any defense, as the pro-Clinton message outfit Correct the Record has done in the case of Clinton’s age and other issues.

“Yes, there have been attacks on her after the midterms, but they have been hitting her hard for over a year,” said Correct the Record communications director Adrienne Elrod. “They are trying as hard as possible to make sure she’s not the nominee, and the reason they are doing that is that they don’t want to run against her.”

But from the point of view of many Republicans, the attacks serve a simple purpose: to damage the presumptive Democratic nominee.

In 2008, Republicans benefitted from the bitter primary fight between Clinton and Barack Obama, which aired a lot of dirty laundry. Republicans now need to keep up the pressure on Clinton during the Democratic primary season if Clinton faces no serious opposition, Jones said.

“The party needs to keep applying pressure to her and keeping her and her team off balance, particularly if she’s running against Larry, Curly and Moe” on the Democratic side, Jones said.

Clinton has said she is still considering whether to run and will probably decide after Jan. 1. She is quietly meeting with potential donors and possible campaign strategists, and is widely expected to make an official announcement by mid-February. She has given no sign that Republican attacks figure into that calculus.

“The other side has no choice but to be constantly negative, because they know that Hillary has widespread grass-roots support and is the strongest, most qualified candidate if she decides to run,” said Seth Bringman, spokesman for the pro-Clinton Ready for Hillary super PAC. “The best way for her supporters to respond is by doubling down on the positive effort to build a grass-roots army of supporters to help her win.”

Some of the attacks are personal: Walker, 47, said this week that he could run for president in 20 years and be the same age as Clinton is now. Some are about Clinton’s policies and politics, as articulated over her long career and on the stump for fellow Democrats in the midterms.

Even before the full extent of the Democratic rout was known on election night, Paul tweeted a picture of Clinton side-hugging losing Kentucky Senate candidate Alison Lundergan Grimes. He labeled it with the hashtag “#Hillaryslosers.”

Republicans are hoping that Clinton is tainted by her party’s midterm defeat. They are also attacking her on issues such as Asia policy, the Keystone XL pipeline and the 2012 attacks in Benghazi, Libya.

Paul began focusing on Clinton before she stepped down as secretary of state. At a Senate hearing in January 2013, Paul told Clinton he would have fired her over the deaths of four Americans in Benghazi. Paul later suggested that the episode should disqualify Clinton from higher office.

Paul, 51, and some other Republicans have also suggested Clinton may not be up to the physical rigors of a second run for president. She suffered a head injury in a fall two years ago that sidelined her for weeks but has said she has no lingering effects.

Republican strategist Karl Rove came under fire this year for seeming to suggest that she had suffered a “traumatic brain injury” in the fall; he later disavowed intending to say that.

In 2015, as Republican presidential hopefuls compete against each other, the RNC’s role will be to “reintroduce Clinton” in a negative light, said RNC communications director Sean Spicer. “It’s not a silver bullet, but it’s chink after chink after chink in her armor,” he said.

The RNC’s war room has been trained on Clinton for months and made much of Clinton’s stumbles during interviews to promote her June memoir, “Hard Choices.”

America Rising, the GOP research and communications shop founded by former presidential campaign operatives, has been leading the attack against Clinton for more than a year. Tim Miller, the group’s executive director, said Clinton’s “limbo state” — before the expected announcement of her candidacy — makes her especially susceptible to hits from Republicans.

“It’s an opportunity for our side to continue to define her and to continue to highlight her weaknesses before she has a campaign infrastructure that’s fully up and operational,” Miller said.

America Rising took another swing at Clinton on Tuesday over the Keystone oil pipeline, which was rejected by the Senate on Tuesday night.

The project has divided Democrats, and President Obama has signaled that he is leaning against approving the huge project to pump oil from Canada to the Gulf of Mexico. Clinton has declined to offer a public opinion on Keystone, arguing that her connection to the State Department — which is leading the Obama administration’s review of the project — prevents her from taking sides.

“She wrote a book called ‘Hard Choices,’ but she wouldn’t take an opinion on the Keystone pipeline,” Miller said. “She may be the only person in America without a position on the Keystone pipeline at this point.”

A Clinton spokesman did not respond to a request for comment.

For Clinton, however, there is little apparent upside to taking a stance now. If she comes out in favor of the pipeline, she will anger environmental and climate activists, including megadonor Tom Steyer and many other major Democratic contributors. If she opposes it, she will be at odds with many business leaders.

Republicans intend to make life similarly uncomfortable for Clinton by combing through her State Department tenure and dipping into the scandals and controversies of her husband’s administration. Of course, they will also seek ways to tie Clinton to Obama, whose popularity is stuck underwater.

“Like anything in life, preparation is the key to success,” Priebus said. “I’m a big believer that the most prepared team wins.”